diff --git a/.markdownlint.yml b/.markdownlint.yml
new file mode 100644
index 0000000..4572cb2
--- /dev/null
+++ b/.markdownlint.yml
@@ -0,0 +1,4 @@
+# ref. https://github.com/DavidAnson/markdownlint
+default: true
+MD013:          # Line length
+  line_length: 240