diff --git a/README.md b/README.md
index cf8df1c..390a6c9 100644
--- a/README.md
+++ b/README.md
@@ -54,6 +54,9 @@ Default is `run`.
 Enable runtime debug output. Default is `false`.
 - `verbose`  
 Enable detailed progress output. Default is `false`.
+- `version`
+This parameter specifies the version of runn.  
+If this parameter is omitted, runn-action automatically selects and runs the same version of runn as its own version.
 - `fail-fast`  
 Terminates the process if a step in the scenario fails in the middle of a step. Default is `false`.
 - `skip-test`