diff --git a/.flake8 b/.flake8
index 6deafc261..7da1f9608 100644
--- a/.flake8
+++ b/.flake8
@@ -1,2 +1,2 @@
 [flake8]
-max-line-length = 120
+max-line-length = 100
diff --git a/pyproject.toml b/pyproject.toml
index a47d0e442..56ce77371 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,8 +1,8 @@
 [tool.black]
 target-version = ['py38']
-line-length = 120
+line-length = 100
 include = '\.pyi?$'
 
 # TODO: .flake8 を消してこちらに移植する
 # [tool.flake8]
-# max-line-length = 120
+# max-line-length = 100