diff --git a/README.md b/README.md
index 0fd47bedb7..67d1c38bd8 100644
--- a/README.md
+++ b/README.md
@@ -35,6 +35,9 @@ For additional features
 
 Environments under Python 2.7.12 and 3.6.0 are tested.
 
+The HEAD of the master branch is developed for Chainer v2.
+For users using Chainer v1, please use version 0.4.10, which can be installed by `pip install chainercv==0.4.10`.
+
 
 # Features