diff --git a/stock/analysis/Common.py b/stock/analysis/Common.py
index 7523898..9377d7b 100644
--- a/stock/analysis/Common.py
+++ b/stock/analysis/Common.py
@@ -634,7 +634,7 @@ class Common:
                         check = True
                         break
                 # 볼린저 밴드 %B와 MFI로 매수 시점
-                if len(stock['pb']) > 2 and len(stock['mfi']) > 2:
+                if len(stock['pb']) > 2 and stock['pb'][i+1] is not None and len(stock['mfi']) > 2 and stock['mfi'][i] is not None:
                     if 80 < stock['pb'][i+1] and 80 < stock['mfi'][i]:
                         check = True
                         break