diff --git a/free-programming-books-ja.md b/free-programming-books-ja.md
index 2ba8778f7558639213804c59ea6dede677a876e1..980640077f9f4c2da0ac7d906cb3faddb9d8f95a 100644
--- a/free-programming-books-ja.md
+++ b/free-programming-books-ja.md
@@ -25,6 +25,9 @@
 * [Erlang](#erlang)
 * [Git](#git)
 * [Go](#go)
+* [Groovy](#groovy)
+    * [Gradle](#gradle)
+    * [Grails](#grails)
 * [Haskell](#haskell)
 * [Haxe](#haxe)
 * [iOS](#ios)