diff --git a/cpprefjp/static/robots.txt b/cpprefjp/static/robots.txt
index aba2387..b4d507b 100644
--- a/cpprefjp/static/robots.txt
+++ b/cpprefjp/static/robots.txt
@@ -1,2 +1,3 @@
 User-agent: *
+Disallow: /site/gen/
 Sitemap: http://cpprefjp.github.io/sitemap.xml