diff --git a/src/main/kotlin/com/ixfp/gitmon/client/github/GithubApiService.kt b/src/main/kotlin/com/ixfp/gitmon/client/github/GithubApiService.kt
index 3c493a3..99708ff 100644
--- a/src/main/kotlin/com/ixfp/gitmon/client/github/GithubApiService.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/client/github/GithubApiService.kt
@@ -59,13 +59,14 @@ class GithubApiService(
         githubUsername: String,
         repo: String,
         path: String,
-        commitMessage: String = "Upsert File by API",
+        commitMessage: String,
+        sha: String = "",
     ): GithubContent {
         val request =
             GithubUpsertFileRequest(
-                message = "Add New File",
+                message = commitMessage,
                 content = Base64Encoder.encodeBase64(content),
-                sha = "",
+                sha = sha,
             )
         val response =
             githubResourceApiClient.upsertFile(
diff --git a/src/main/kotlin/com/ixfp/gitmon/controller/IPostingController.kt b/src/main/kotlin/com/ixfp/gitmon/controller/IPostingController.kt
index 7a5857d..68a3d6f 100644
--- a/src/main/kotlin/com/ixfp/gitmon/controller/IPostingController.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/controller/IPostingController.kt
@@ -103,4 +103,11 @@ interface IPostingController {
         githubUsername: String,
         postingId: Long,
     ): ResponseEntity<ApiResponseBody<PostingReadDto>>
+
+    fun updatePosting(
+        id: Long,
+        title: String,
+        content: MultipartFile,
+        member: Member,
+    ): ResponseEntity<ApiResponseBody<PostingReadDto>>
 }
diff --git a/src/main/kotlin/com/ixfp/gitmon/controller/PostingController.kt b/src/main/kotlin/com/ixfp/gitmon/controller/PostingController.kt
index 268d5d7..98d76c7 100644
--- a/src/main/kotlin/com/ixfp/gitmon/controller/PostingController.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/controller/PostingController.kt
@@ -12,6 +12,7 @@ import org.springframework.http.ResponseEntity
 import org.springframework.web.bind.annotation.GetMapping
 import org.springframework.web.bind.annotation.PathVariable
 import org.springframework.web.bind.annotation.PostMapping
+import org.springframework.web.bind.annotation.PutMapping
 import org.springframework.web.bind.annotation.RequestAttribute
 import org.springframework.web.bind.annotation.RequestMapping
 import org.springframework.web.bind.annotation.RequestParam
@@ -37,6 +38,20 @@ class PostingController(
         return ApiResponseHelper.created(posting)
     }
 
+    @PutMapping(
+        consumes = [MediaType.MULTIPART_FORM_DATA_VALUE],
+    )
+    override fun updatePosting(
+        @RequestParam id: Long,
+        @RequestParam title: String,
+        @RequestPart content: MultipartFile,
+        @RequestAttribute(AUTHENTICATED_MEMBER) member: Member,
+    ): ResponseEntity<ApiResponseBody<PostingReadDto>> {
+        val updatedPosting = postingService.update(member, id, title, content)
+        val posting = postingService.findPosting(updatedPosting)
+        return ApiResponseHelper.success(posting)
+    }
+
     @GetMapping("/{exposedMemberId}")
     override fun getPostingList(
         @PathVariable exposedMemberId: String,
diff --git a/src/main/kotlin/com/ixfp/gitmon/db/posting/PostingEntity.kt b/src/main/kotlin/com/ixfp/gitmon/db/posting/PostingEntity.kt
index 15c20df..5f7b009 100644
--- a/src/main/kotlin/com/ixfp/gitmon/db/posting/PostingEntity.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/db/posting/PostingEntity.kt
@@ -13,9 +13,9 @@ class PostingEntity(
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     val id: Long = 0,
-    val title: String,
+    var title: String,
     val refMemberId: Long,
-    val githubFilePath: String,
-    val githubFileSha: String,
-    val githubDownloadUrl: String,
+    var githubFilePath: String,
+    var githubFileSha: String,
+    var githubDownloadUrl: String,
 ) : BaseEntity()
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/CommitMessageGenerator.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/CommitMessageGenerator.kt
new file mode 100644
index 0000000..85a2182
--- /dev/null
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/CommitMessageGenerator.kt
@@ -0,0 +1,19 @@
+package com.ixfp.gitmon.domain.posting
+
+object CommitMessageGenerator {
+    fun createMessage(title: String): String {
+        return "Create \"$title\" - by Gitmon 👾"
+    }
+
+    fun updateMessage(title: String): String {
+        return "Update \"$title\" - by Gitmon 👾"
+    }
+
+    fun deleteMessage(title: String): String {
+        return "Delete \"$title\" - by Gitmon 👾"
+    }
+
+    fun imageUploadMessage(): String {
+        return "Upload image - by Gitmon 👾"
+    }
+}
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/Posting.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/Posting.kt
new file mode 100644
index 0000000..b0f76b3
--- /dev/null
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/Posting.kt
@@ -0,0 +1,14 @@
+package com.ixfp.gitmon.domain.posting
+
+import java.time.LocalDateTime
+
+data class Posting(
+    val id: Long,
+    val title: String,
+    val refMemberId: Long,
+    val githubFilePath: String,
+    val githubFileSha: String,
+    val githubDownloadUrl: String,
+    val createdAt: LocalDateTime,
+    val updatedAt: LocalDateTime,
+)
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingReader.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingReader.kt
index 1924b8a..beb5066 100644
--- a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingReader.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingReader.kt
@@ -11,20 +11,23 @@ import org.springframework.stereotype.Component
 class PostingReader(
     private val postingRepository: PostingRepository,
 ) {
-    fun findPostingListByMemberId(memberId: Long): List<PostingReadDto> {
-        return postingRepository.findByRefMemberId(memberId).map { toPostingItem(it) }
+    fun findPostingListByMemberId(memberId: Long): List<Posting> {
+        return postingRepository.findByRefMemberId(memberId).map { toPosting(it) }
     }
 
-    fun findPostingById(postingId: Long): PostingReadDto {
+    fun findPostingById(postingId: Long): Posting {
         return postingRepository.findById(postingId)
             .orElseThrow { IllegalArgumentException("Posting with id $postingId not found") }
-            .let { toPostingItem(it) }
+            .let { toPosting(it) }
     }
 
-    private fun toPostingItem(entity: PostingEntity): PostingReadDto {
-        return PostingReadDto(
+    private fun toPosting(entity: PostingEntity): Posting {
+        return Posting(
             id = entity.id,
             title = entity.title,
+            refMemberId = entity.refMemberId,
+            githubFilePath = entity.githubFilePath,
+            githubFileSha = entity.githubFileSha,
             githubDownloadUrl = entity.githubDownloadUrl,
             createdAt = entity.createdAt,
             updatedAt = entity.updatedAt,
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingService.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingService.kt
index f317437..88523da 100644
--- a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingService.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingService.kt
@@ -5,6 +5,7 @@ import com.ixfp.gitmon.common.aop.WrapWith
 import com.ixfp.gitmon.domain.member.Member
 import com.ixfp.gitmon.domain.member.MemberService
 import com.ixfp.gitmon.domain.posting.exception.InvalidImageExtensionException
+import com.ixfp.gitmon.domain.posting.exception.PostingAuthorizationException
 import com.ixfp.gitmon.domain.posting.exception.PostingExceptionStrategy
 import com.ixfp.gitmon.domain.posting.exception.PostingRepositoryNotFoundException
 import io.github.oshai.kotlinlogging.KotlinLogging.logger
@@ -23,6 +24,7 @@ class PostingService(
     fun findPostingListByMemberExposedId(memberExposedId: String): List<PostingReadDto> {
         val member = memberService.getMemberByExposedId(memberExposedId)
         return postingReader.findPostingListByMemberId(member.id)
+            .map { toPostingReadDto(it) }
     }
 
     fun findPostingListByGithubUsername(githubUsername: String): List<PostingReadDto> {
@@ -32,16 +34,16 @@ class PostingService(
         val postingList = postingReader.findPostingListByMemberId(member.id)
 
         log.info { "[PostingService] 포스팅 목록 조회 완료. githubUsername=${member.githubUsername}, postingList.size=${postingList.size}" }
-        return postingList
+        return postingList.map { toPostingReadDto(it) }
     }
 
-    fun findPosting(postingId: Long): PostingReadDto? {
+    fun findPosting(postingId: Long): PostingReadDto {
         log.info { "[PostingService] 포스팅 조회 시작. postingId=$postingId" }
 
         val posting = postingReader.findPostingById(postingId)
 
         log.info { "[PostingService] 포스팅 조회 완료. posting=$posting" }
-        return posting
+        return toPostingReadDto(posting)
     }
 
     fun findPosting(
@@ -56,7 +58,7 @@ class PostingService(
                 .find { it.id == postingId }
 
         log.info { "[PostingService] 포스팅 조회 완료. githubUsername=${member.githubUsername}, posting=$posting" }
-        return posting
+        return posting?.let { toPostingReadDto(it) }
     }
 
     fun create(
@@ -78,6 +80,7 @@ class PostingService(
                 githubUsername = member.githubUsername,
                 repo = member.repoName,
                 path = "$title.md",
+                commitMessage = CommitMessageGenerator.createMessage(title = title),
             )
 
         val savedPostingId =
@@ -95,6 +98,48 @@ class PostingService(
         return savedPostingId
     }
 
+    fun update(
+        member: Member,
+        postingId: Long,
+        title: String,
+        content: MultipartFile,
+    ): Long {
+        log.info { "PostingService#update start. member=$member, postingId=$postingId, title=$title, content.size=${content.size}" }
+        val posting = postingReader.findPostingById(postingId)
+
+        if (posting.refMemberId != member.id) {
+            log.warn { "본인이 작성하지 않은 포스팅에 대한 수정 시도. memberId=${member.id}, postingId=$postingId" }
+            throw PostingAuthorizationException()
+        }
+
+        val githubAccessToken = memberService.getGithubAccessTokenById(member.id)
+
+        val githubContent =
+            githubApiService.upsertFile(
+                githubAccessToken = githubAccessToken,
+                content = content,
+                githubUsername = member.githubUsername,
+                repo = member.repoName ?: throw PostingRepositoryNotFoundException(),
+                path = "$title.md",
+                commitMessage = CommitMessageGenerator.updateMessage(title = title),
+                sha = posting.githubFileSha,
+            )
+
+        val updatedPostingId =
+            postingWriter.update(
+                postingId,
+                PostingUpdateDto(
+                    title = title,
+                    githubFilePath = githubContent.path,
+                    githubFileSha = githubContent.sha,
+                    githubDownloadUrl = githubContent.download_url,
+                ),
+            )
+
+        log.info { "PostingService#update end. updatedPostingId=$updatedPostingId, contentSha=${githubContent.sha}" }
+        return updatedPostingId
+    }
+
     private fun uploadImage(
         member: Member,
         content: MultipartFile,
@@ -116,6 +161,7 @@ class PostingService(
                 githubUsername = member.githubUsername,
                 repo = member.repoName,
                 path = path,
+                commitMessage = CommitMessageGenerator.imageUploadMessage(),
             )
 
         return githubContent.download_url
@@ -136,6 +182,16 @@ class PostingService(
         return null
     }
 
+    private fun toPostingReadDto(posting: Posting): PostingReadDto {
+        return PostingReadDto(
+            id = posting.id,
+            title = posting.title,
+            githubDownloadUrl = posting.githubDownloadUrl,
+            createdAt = posting.createdAt,
+            updatedAt = posting.updatedAt,
+        )
+    }
+
     companion object {
         private val log = logger {}
     }
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingUpdateDto.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingUpdateDto.kt
new file mode 100644
index 0000000..173a90a
--- /dev/null
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingUpdateDto.kt
@@ -0,0 +1,8 @@
+package com.ixfp.gitmon.domain.posting
+
+data class PostingUpdateDto(
+    val title: String,
+    val githubFilePath: String,
+    val githubFileSha: String,
+    val githubDownloadUrl: String,
+)
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingWriter.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingWriter.kt
index 517826c..16477d4 100644
--- a/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingWriter.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/PostingWriter.kt
@@ -4,6 +4,7 @@ import com.ixfp.gitmon.common.aop.WrapWith
 import com.ixfp.gitmon.db.exception.DbExceptionStrategy
 import com.ixfp.gitmon.db.posting.PostingEntity
 import com.ixfp.gitmon.db.posting.PostingRepository
+import org.springframework.data.repository.findByIdOrNull
 import org.springframework.stereotype.Component
 
 @WrapWith(DbExceptionStrategy::class)
@@ -24,4 +25,22 @@ class PostingWriter(
 
         return saved.id
     }
+
+    fun update(
+        postingId: Long,
+        postingUpdateDto: PostingUpdateDto,
+    ): Long {
+        val postingEntity =
+            postingRepository.findByIdOrNull(postingId)
+                ?: throw IllegalArgumentException("Posting with id $postingId not found")
+
+        postingEntity.title = postingUpdateDto.title
+        postingEntity.githubFilePath = postingUpdateDto.githubFilePath
+        postingEntity.githubFileSha = postingUpdateDto.githubFileSha
+        postingEntity.githubDownloadUrl = postingUpdateDto.githubDownloadUrl
+
+        val updated = postingRepository.save(postingEntity)
+
+        return updated.id
+    }
 }
diff --git a/src/main/kotlin/com/ixfp/gitmon/domain/posting/exception/PostingExceptions.kt b/src/main/kotlin/com/ixfp/gitmon/domain/posting/exception/PostingExceptions.kt
index 3c60937..ba6a6a1 100644
--- a/src/main/kotlin/com/ixfp/gitmon/domain/posting/exception/PostingExceptions.kt
+++ b/src/main/kotlin/com/ixfp/gitmon/domain/posting/exception/PostingExceptions.kt
@@ -17,6 +17,11 @@ class InvalidImageExtensionException(
     cause: Throwable? = null,
 ) : PostingException(message, cause)
 
+class PostingAuthorizationException(
+    message: String = "게시글에 대한 권한이 없습니다.",
+    cause: Throwable? = null,
+) : PostingException(message, cause)
+
 class PostingUnexpectedException(
     message: String = "예상치 못한 게시글 도메인 예외가 발생했습니다.",
     cause: Throwable? = null,