diff --git a/GUIDE.md b/GUIDE.md
index e60046ab..a064c4f5 100644
--- a/GUIDE.md
+++ b/GUIDE.md
@@ -3,12 +3,13 @@
 <!-- toc -->
 
 - [Installation](#installation)
+  - [GitHub Token](#github-token)
   - [Before running Shipjs](#before-running-shipjs)
   - [Dry Mode](#dry-mode)
 - [On your local machine](#on-your-local-machine)
 - [Automate Part 3 (`shipjs trigger`) on your CI](#automate-part-3-shipjs-trigger-on-your-ci)
   - [NPM Token](#npm-token)
-  - [GitHub Token](#github-token)
+  - [GitHub Token](#github-token-1)
 - [Useful Configurations](#useful-configurations)
   - [`mergeStrategy`](#mergestrategy)
     - [`toSameBranch` strategy](#tosamebranch-strategy)
@@ -54,6 +55,22 @@ Add the following to the `scripts` section in your `package.json`.
 }
 ```
 
+### GitHub Token
+
+GitHub token is used in both `shipjs prepare` and `shipjs trigger`.
+
+1. Go to https://github.com/settings/tokens/new
+2. Check "repo(Full control of private repositories)"
+3. Generate/copy the token
+
+You can put it in the following two ways:
+
+1. Prepend it in your command like: `GITHUB_TOKEN=xxx shipjs prepare`
+2. Create a file named ".env" and put the following content: `GITHUB_TOKEN=xxx`
+   (".env" should not be committed. Add it to ".gitignore".)
+
+If you automate flows in your CI, you can add the token to Environment Variable section in your CI service.
+
 ### Before running Shipjs
 
 Shipjs compares previous version.
diff --git a/packages/shipjs/src/flow/prepare.js b/packages/shipjs/src/flow/prepare.js
index 9be06892..a865da99 100644
--- a/packages/shipjs/src/flow/prepare.js
+++ b/packages/shipjs/src/flow/prepare.js
@@ -18,6 +18,7 @@ import commitChanges from '../step/prepare/commitChanges';
 import createPullRequest from '../step/prepare/createPullRequest';
 import notifyPrepared from '../step/prepare/notifyPrepared';
 import pushToStagingBranch from '../step/prepare/pushToStagingBranch';
+import checkGitHubToken from '../step/checkGitHubToken';
 import finished from '../step/finished';
 
 import { print } from '../util';
@@ -40,6 +41,7 @@ async function prepare({
     printDryRunBanner();
   }
   printDeprecated({ firstRelease, releaseCount });
+  checkGitHubToken({ dryRun });
   const config = loadConfig(dir);
   const { currentVersion, baseBranch } = validate({ config, dir });
   validateMergeStrategy({ config });
diff --git a/packages/shipjs/src/flow/release.js b/packages/shipjs/src/flow/release.js
index 94272d56..6c684193 100644
--- a/packages/shipjs/src/flow/release.js
+++ b/packages/shipjs/src/flow/release.js
@@ -14,6 +14,7 @@ import createGitTag from '../step/release/createGitTag';
 import gitPush from '../step/release/gitPush';
 import createGitHubRelease from '../step/release/createGitHubRelease';
 import notifyReleaseSuccess from '../step/release/notifyReleaseSuccess';
+import checkGitHubToken from '../step/checkGitHubToken';
 import finished from '../step/finished';
 import { detectYarn } from '../util';
 
@@ -25,6 +26,7 @@ async function release({ help = false, dir = '.', dryRun = false }) {
   if (dryRun) {
     printDryRunBanner();
   }
+  checkGitHubToken({ dryRun });
   const config = loadConfig(dir);
   const { remote } = config;
   const { currentVersion: version } = validate({ config, dir });
diff --git a/packages/shipjs/src/step/checkGitHubToken.js b/packages/shipjs/src/step/checkGitHubToken.js
new file mode 100644
index 00000000..7548f35a
--- /dev/null
+++ b/packages/shipjs/src/step/checkGitHubToken.js
@@ -0,0 +1,21 @@
+import runStep from './runStep';
+import { print, exitProcess } from '../util';
+import { error } from '../color';
+
+export default ({ dryRun }) =>
+  runStep({ title: 'Checking GITHUB_TOKEN' }, () => {
+    if (process.env.GITHUB_TOKEN) {
+      return;
+    }
+    print(
+      error('You need to specify GITHUB_TOKEN as an environment variable.')
+    );
+    print('  1. GITHUB_TOKEN=xxx shipjs ...');
+    print('     or');
+    print('  2. Create a file named ".env" and put the following content:');
+    print('     GITHUB_TOKEN=xxx');
+    print('     (".env" should not be committed. Add it to ".gitignore".)');
+    if (!dryRun) {
+      exitProcess(1);
+    }
+  });