diff --git a/README.md b/README.md
index 15e28da..1d4ed52 100644
--- a/README.md
+++ b/README.md
@@ -14,7 +14,7 @@ code review experience.
 
 ### `github_token`
 
-**Required**. Must be in form of `github_token: ${{ secrets.github_token }}`'.
+Optional. `${{ github.token }}` is used by default.
 
 ### `level`
 
diff --git a/action.yml b/action.yml
index 686a28c..313d8cb 100644
--- a/action.yml
+++ b/action.yml
@@ -4,7 +4,7 @@ author: 'haya14busa (reviewdog)'
 inputs:
   github_token:
     description: 'GITHUB_TOKEN.'
-    required: true
+    default: '${{ github.token }}'
   level:
     description: 'Report level for reviewdog [info,warning,error]'
     default: 'error'