diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 12b2c18..91382c8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -9,7 +9,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: denoland/setup-deno@v1
         with:
-          deno-version: "1.28.1"
+          deno-version: "1.32.3"
       - name: Check fmt
         run: deno fmt --check
       - name: Run lint
diff --git a/.github/workflows/udd.yml b/.github/workflows/udd.yml
index b2ea0bc..37df0d9 100644
--- a/.github/workflows/udd.yml
+++ b/.github/workflows/udd.yml
@@ -12,7 +12,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: denoland/setup-deno@v1
         with:
-          deno-version: "1.28.1"
+          deno-version: "1.32.3"
       - name: Update dependencies
         run: >
           deno run --allow-net --allow-read --allow-write=deps/
diff --git a/deps/hash.ts b/deps/hash.ts
new file mode 100644
index 0000000..6780d11
--- /dev/null
+++ b/deps/hash.ts
@@ -0,0 +1 @@
+export { Md5 } from "https://deno.land/std@0.160.0/hash/md5.ts#=";
diff --git a/rest/mod.ts b/rest/mod.ts
index c204812..c11c9d1 100644
--- a/rest/mod.ts
+++ b/rest/mod.ts
@@ -14,3 +14,4 @@ export * from "./auth.ts";
 export * from "./util.ts";
 export * from "./error.ts";
 export * from "./getCodeBlocks.ts";
+export * from "./uploadToGCS.ts";
diff --git a/rest/uploadToGCS.ts b/rest/uploadToGCS.ts
new file mode 100644
index 0000000..05642a0
--- /dev/null
+++ b/rest/uploadToGCS.ts
@@ -0,0 +1,169 @@
+import { cookie, getCSRFToken } from "./auth.ts";
+import { BaseOptions, ExtendedOptions, Result, setDefaults } from "./util.ts";
+import { makeError, UnexpectedResponseError } from "./error.ts";
+import type { ErrorLike, NotFoundError } from "../deps/scrapbox-rest.ts";
+import { Md5 } from "../deps/hash.ts";
+
+/** uploadしたファイルのメタデータ */
+export interface GCSFile {
+  /** uploadしたファイルのURL */
+  embedUrl: string;
+
+  /** uploadしたファイルの名前 */
+  originalName: string;
+}
+
+/** 任意のファイルをscrapbox.ioにuploadする
+ *
+ * @param file uploadしたいファイル
+ * @param projectId upload先projectのid
+ * @return 成功したら、ファイルのクラウド上のURLなどが返ってくる
+ */
+export const uploadToGCS = async (
+  file: File,
+  projectId: string,
+  options?: ExtendedOptions,
+): Promise<
+  Result<GCSFile, GCSError | NotFoundError | FileCapacityError | ErrorLike>
+> => {
+  const md5 = new Md5().update(await file.arrayBuffer()).toString();
+  const res = await uploadRequest(file, projectId, md5, options);
+  if (!res.ok) return res;
+  if ("embedUrl" in res.value) return { ok: true, value: res.value };
+  const res2 = await upload(res.value.signedUrl, file, options);
+  if (!res2.ok) return res2;
+  return verify(projectId, res.value.fileId, md5, options);
+};
+
+/** 容量を使い切ったときに発生するerror */
+export interface FileCapacityError extends ErrorLike {
+  name: "FileCapacityError";
+}
+
+interface UploadRequest {
+  /** upload先URL */
+  signedUrl: string;
+
+  /** uploadしたファイルに紐付けられる予定のfile id */
+  fileId: string;
+}
+
+/** ファイルのuploadを要求する
+ *
+ * @param file uploadしたいファイル
+ * @param projectId upload先projectのid
+ * @param md5 uploadしたいファイルのMD5 hash (16進数)
+ * @return すでにuploadされていればファイルのURLを、まだの場合はupload先URLを返す
+ */
+const uploadRequest = async (
+  file: File,
+  projectId: string,
+  md5: string,
+  init?: ExtendedOptions,
+): Promise<Result<GCSFile | UploadRequest, FileCapacityError | ErrorLike>> => {
+  const { sid, hostName, fetch, csrf } = setDefaults(init ?? {});
+  const body = {
+    md5,
+    size: file.size,
+    contentType: file.type,
+    name: file.name,
+  };
+  const token = csrf ?? await getCSRFToken();
+  const req = new Request(
+    `https://${hostName}/api/gcs/${projectId}/upload-request`,
+    {
+      method: "POST",
+      body: JSON.stringify(body),
+      headers: {
+        "Content-Type": "application/json;charset=utf-8",
+        "X-CSRF-TOKEN": token,
+        ...(sid ? { Cookie: cookie(sid) } : {}),
+      },
+    },
+  );
+  const res = await fetch(req);
+  if (!res.ok) {
+    return makeError(res);
+  }
+  return { ok: true, value: await res.json() };
+};
+
+/** Google Cloud Storage XML APIのerror
+ *
+ * `message`には[この形式](https://cloud.google.com/storage/docs/xml-api/reference-status#http-status-and-error-codes)のXMLが入る
+ */
+export interface GCSError extends ErrorLike {
+  name: "GCSError";
+}
+
+/** ファイルをuploadする */
+const upload = async (
+  signedUrl: string,
+  file: File,
+  init?: BaseOptions,
+): Promise<Result<undefined, GCSError>> => {
+  const { sid, fetch } = setDefaults(init ?? {});
+  const res = await fetch(
+    signedUrl,
+    {
+      method: "PUT",
+      body: file,
+      headers: {
+        "Content-Type": file.type,
+        ...(sid ? { Cookie: cookie(sid) } : {}),
+      },
+    },
+  );
+  if (!res.ok) {
+    if (res.headers.get("Content-Type")?.includes?.("/xml")) {
+      return {
+        ok: false,
+        value: {
+          name: "GCSError",
+          message: await res.text(),
+        },
+      };
+    }
+    throw new UnexpectedResponseError(res);
+  }
+  return { ok: true, value: undefined };
+};
+
+/** uploadしたファイルの整合性を確認する */
+const verify = async (
+  projectId: string,
+  fileId: string,
+  md5: string,
+  init?: ExtendedOptions,
+): Promise<Result<GCSFile, NotFoundError>> => {
+  const { sid, hostName, fetch, csrf } = setDefaults(init ?? {});
+  const token = csrf ?? await getCSRFToken();
+  const req = new Request(
+    `https://${hostName}/api/gcs/${projectId}/verify`,
+    {
+      method: "POST",
+      body: JSON.stringify({ md5, fileId }),
+      headers: {
+        "Content-Type": "application/json;charset=utf-8",
+        "X-CSRF-TOKEN": token,
+        ...(sid ? { Cookie: cookie(sid) } : {}),
+      },
+    },
+  );
+  const res = await fetch(req);
+  if (!res.ok) {
+    try {
+      if (res.status === 404) {
+        return {
+          ok: false,
+          value: { name: "NotFoundError", message: (await res.json()).message },
+        };
+      }
+    } catch (_) {
+      throw new UnexpectedResponseError(res);
+    }
+    throw new UnexpectedResponseError(res);
+  }
+  const gcs = await res.json();
+  return { ok: true, value: gcs };
+};