diff --git a/src/api/http-error.test.ts b/src/api/http-error.test.ts
index 190dd6c..b693de9 100644
--- a/src/api/http-error.test.ts
+++ b/src/api/http-error.test.ts
@@ -1,8 +1,58 @@
 import { HttpError } from '~/api/http-error'
 import { useMockedUrlFetchApp } from '~/api/test-helper'
 
-test('HttpError', () => {
-  const res = useMockedUrlFetchApp(403, '{"message": "Forbidden"}')()
-  const error = new HttpError('https://example.com', res)
-  expect(error instanceof HttpError).toBeTruthy()
+describe('HttpError', () => {
+  test('#isInvalidTestingRequest', () => {
+    const res = useMockedUrlFetchApp(400, '{"message":"Testing apikey is not allowed"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isInvalidTestingRequest()).toBeTruthy()
+  })
+
+  test('#isInvalidTokenRequest (true)', () => {
+    const res = useMockedUrlFetchApp(403, '{"message":"Forbidden"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isInvalidTokenRequest()).toBeTruthy()
+  })
+
+  test('#isInvalidTokenRequest (false)', () => {
+    const res = useMockedUrlFetchApp(403, '{"message":"Some message"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isInvalidTokenRequest()).toBeFalsy()
+  })
+
+  test('#isMonthlyLimitExceeded (true)', () => {
+    const res = useMockedUrlFetchApp(403, '{"message":"Some message"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isMonthlyLimitExceeded()).toBeTruthy()
+  })
+
+  test('#isMonthlyLimitExceeded (false)', () => {
+    const res = useMockedUrlFetchApp(403, '{"message":"Forbidden"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isMonthlyLimitExceeded()).toBeFalsy()
+  })
+
+  test('#isApiQuotaExceeded', () => {
+    const res = useMockedUrlFetchApp(404, '{"message":"Not found"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isResourceNotFound()).toBeTruthy()
+  })
+
+  test('#isApiQuotaExceeded', () => {
+    const res = useMockedUrlFetchApp(429, '{"message":"Rate Limitted"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.isApiQuotaExceeded()).toBeTruthy()
+  })
+
+  test('#is4xxError', () => {
+    const res = useMockedUrlFetchApp(403, '{"message":"Forbidden"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.is4xxError()).toBeTruthy()
+  })
+
+  test('#is5xxError', () => {
+    const res = useMockedUrlFetchApp(500, '{"message":"Internal server error"}')()
+    const error = new HttpError('https://example.com', res)
+    expect(error.is5xxError()).toBeTruthy()
+  })
 })
diff --git a/src/api/http-error.ts b/src/api/http-error.ts
index 96c4c7c..ec2661f 100644
--- a/src/api/http-error.ts
+++ b/src/api/http-error.ts
@@ -12,19 +12,19 @@ export class HttpError implements Error {
   public isInvalidTestingRequest(): boolean {
     const content = this.response.getContentText()
     return (
-      content === '{"message":"Testing Apikey is only allowed to ticker ending with \\"01\\""}' ||
-      content === '{"message":"Testing apikey is not allowed"}' ||
-      content === '{"message":"Trial request only supports ticker ending \'01\'"}'
+      this.response.getResponseCode() === 400 &&
+      (content === '{"message":"Testing Apikey is only allowed to ticker ending with \\"01\\""}' ||
+        content === '{"message":"Testing apikey is not allowed"}' ||
+        content === '{"message":"Trial request only supports ticker ending \'01\'"}')
     )
   }
 
   public isInvalidTokenRequest(): boolean {
-    const content = this.response.getContentText()
-    return content === '{"message":"Forbidden"}'
+    return this.response.getResponseCode() === 403 && this.response.getContentText() === '{"message":"Forbidden"}'
   }
 
   public isMonthlyLimitExceeded(): boolean {
-    return !this.isInvalidTokenRequest() && this.response.getResponseCode() === 403
+    return this.response.getResponseCode() === 403 && !this.isInvalidTokenRequest()
   }
 
   public isResourceNotFound(): boolean {
@@ -35,10 +35,14 @@ export class HttpError implements Error {
     return this.response.getResponseCode() === 429
   }
 
-  public isBadRequest(): boolean {
+  public is4xxError(): boolean {
     return Math.floor(this.response.getResponseCode() / 100) === 4
   }
 
+  public is5xxError(): boolean {
+    return Math.floor(this.response.getResponseCode() / 100) === 5
+  }
+
   public toString(): string {
     return this.message
   }
diff --git a/src/api/v3/client.test.ts b/src/api/v3/client.test.ts
index d1398b2..20ab39f 100644
--- a/src/api/v3/client.test.ts
+++ b/src/api/v3/client.test.ts
@@ -15,16 +15,6 @@ import { YearQuarterParam } from '~/fiscal-periods/year-quarter-param'
 import { YearQuarterRange } from '~/fiscal-periods/year-quarter-range'
 
 describe('BuffettCodeApiClientV3', () => {
-  test('HttpError#isInvalidTestingRequest', () => {
-    const res1 = useMockedUrlFetchApp(200, '{"message":"Testing apikey is not allowed"}')()
-    const error1 = new HttpError('https://example.com', res1)
-    expect(error1.isInvalidTestingRequest()).toBeTruthy()
-
-    const res2 = useMockedUrlFetchApp(403, '{"message": "Forbidden"}')()
-    const error2 = new HttpError('https://example.com', res2)
-    expect(error2.isInvalidTestingRequest()).toBeFalsy()
-  })
-
   test('request', () => {
     const mockFetch = useMockedUrlFetchApp(200, '{"message": "this is a message"}')
 
@@ -45,7 +35,7 @@ describe('BuffettCodeApiClientV3', () => {
   })
 
   test('request when testing apikey error', () => {
-    useMockedUrlFetchApp(200, '{"message":"Testing Apikey is only allowed to ticker ending with \\"01\\""}')
+    useMockedUrlFetchApp(400, '{"message":"Testing Apikey is only allowed to ticker ending with \\"01\\""}')
 
     const request = BuffettCodeApiClientV3['request']
     expect(() => request('http://example.com')).toThrow(HttpError)
diff --git a/src/api/v3/client.ts b/src/api/v3/client.ts
index 2cee063..c4450c0 100644
--- a/src/api/v3/client.ts
+++ b/src/api/v3/client.ts
@@ -19,13 +19,13 @@ export class BuffettCodeApiClientV3 {
     const fullOptions = { ...defaultOptions, ...options }
     const res = UrlFetchApp.fetch(url, fullOptions)
 
-    const code = res.getResponseCode()
-    const content = res.getContentText()
     const error = new HttpError(url, res)
-    if (Math.floor(code / 100) === 4 || Math.floor(code / 100) === 5 || error.isInvalidTestingRequest()) {
+    if (error.is4xxError() || error.is5xxError()) {
       throw error
     }
 
+    const content = res.getContentText()
+    const code = res.getResponseCode()
     let json
     try {
       json = JSON.parse(content)
diff --git a/src/services/error-handler.ts b/src/services/error-handler.ts
index 952b9d4..c1d5d68 100644
--- a/src/services/error-handler.ts
+++ b/src/services/error-handler.ts
@@ -37,7 +37,7 @@ export class ErrorHandler {
       throw new Error('<<データが見つかりません。tickerや期間に間違いがないかご確認ください>>')
     } else if (e.isApiQuotaExceeded()) {
       throw new Error('<<APIの実行回数が上限に達しました>>')
-    } else if (e.isBadRequest()) {
+    } else if (e.is4xxError()) {
       throw new Error(`<<無効なリクエストです (${e.name}: ${e.message})>>`)
     } else {
       console.error('システムエラー', e.name, e.message)