diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 2766cdd0..4f66d3a6 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -2,6 +2,7 @@ name: CI
 
 on:
   push:
+  pull_request:
   schedule:
     - cron: '0 0 1,15 * *' # JST 9:00 on 1st and 15th every month