diff --git a/grade.sh b/grade.sh
index 723f285..789b897 100755
--- a/grade.sh
+++ b/grade.sh
@@ -9,14 +9,28 @@ IS_PASS=true
 
 if [ "$1" == "c" ]; then
     echo "C 채점을 시작합니다."
+    if ! (which gcc >/dev/null); then
+        echo "GCC가 없습니다. 채점을 종료합니다."
+        exit 1
+    fi
 else
     echo "Python 채점을 시작합니다."
+    if ! (which python3 >/dev/null); then
+        if ! (which python >/dev/null); then
+            echo "설치된 python이 없습니다. 채점을 종료합니다."
+            exit 1
+        fi
+    fi
 fi
 
 function python_result() {
     # $1: index of problem, $2: input file, $3: output file
 
-    result=`cat $2 | python ./python/$1.py | tr -d '\r' | tr -d '\t'`
+    if ! (which python3 >/dev/null); then
+        result=`cat $2 | python ./python/$1.py | tr -d '\r' | tr -d '\t'`
+    else
+        result=`cat $2 | python3 ./python/$1.py | tr -d '\r' | tr -d '\t'`
+    fi
     output=`cat $3 | tr -d '\r' | tr -d '\t'`