--- a/eccube/data/class/SC_CartSession.php
+++ b/eccube/data/class/SC_CartSession.php
@@ -163,7 +163,7 @@ class SC_CartSession {
             }
             $quantity = $_SESSION[$this->key][$i]['quantity'];
 
-            $pre_tax = SC_Utils::sfPreTax($price, $arrInfo['tax'], $arrInfo['tax_rule']);
+            $pre_tax = SC_Utils_Ex::sfPreTax($price, $arrInfo['tax'], $arrInfo['tax_rule']);
             $total+= ($pre_tax * $quantity);
         }
         return $total;