diff --git a/materials.html b/materials.html
index 1c80f14..a7794df 100644
--- a/materials.html
+++ b/materials.html
@@ -20,7 +20,7 @@
                 </header><p> </p>
                 <div class="flex flex-2">
                     <article><div class="image fit">
-                            <img src="images/class/OIP.jpg" alt="Pic 01" width="576" height="196"></div>
+                            <img src="images/class/R.png" alt="Pic 01" width="576" height="196"></div>
                         <header><h3>第一次社課</h3>
                         </header><p></p>
                         <footer><a href="doc/class01.pdf" target="_blank"" class="button special">More</a>