diff --git a/webroot/styles/app.css b/webroot/styles/app.css
index b8f6f3ed1..8c20cf2c2 100644
--- a/webroot/styles/app.css
+++ b/webroot/styles/app.css
@@ -358,6 +358,13 @@ header {
   overflow: hidden;
   box-sizing: border-box;
 }
+
+@media screen and (max-width: 600px) {
+  .modal__container {
+    width: 100%;
+  }
+}
+
 .modal__close {
   background: transparent;
   border: 0;