diff --git a/SMILEBASIC/error.d b/SMILEBASIC/error.d
index f07023f..84c92e1 100644
--- a/SMILEBASIC/error.d
+++ b/SMILEBASIC/error.d
@@ -19,6 +19,14 @@ class SmileBasicError : Exception
         super(message);
     }
 }
+class SyntaxError : SmileBasicError
+{
+    this()
+    {
+        this.errnum = 3;
+        super("Syntax error");
+    }
+}
 class TypeMismatch : SmileBasicError
 {
     this()
@@ -43,3 +51,12 @@ class ReturnWithoutGosub : SmileBasicError
         super("RETURN without GOSUB");
     }
 }
+class SubscriptOutOfRange : SmileBasicError
+{
+    this()
+    {
+        this.errnum = 31;
+        super("Subscript out of range");
+    }
+}
+
diff --git a/SMILEBASIC/type.d b/SMILEBASIC/type.d
index ad22132..a120aa5 100644
--- a/SMILEBASIC/type.d
+++ b/SMILEBASIC/type.d
@@ -1,4 +1,5 @@
 module otya.smilebasic.type;
+import otya.smilebasic.error;
 enum ValueType : byte
 {
     Void,//DEF A()ENDの返り値とか未初期化の変数とか
@@ -153,34 +154,50 @@ class Array(T)
     }
     T opIndex(int i1)
     {
+        if(dimCount != 1) throw new SyntaxError();
+        if(i1 >= dim[0]) throw new SubscriptOutOfRange();
         return array[i1];
     }
     T opIndex(int i1, int i2)
     {
+        if(dimCount != 2) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1]) throw new SubscriptOutOfRange();
         return array[i1 * dim[0] + i2];
     }
     T opIndex(int i1, int i2, int i3)
     {
+        if(dimCount != 3) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1] && i3 >= dim[2]) throw new SubscriptOutOfRange();
         return array[i1 * dim[0] * dim[1] + i2 * dim[1] + i3];
     }
     T opIndex(int i1, int i2, int i3, int i4)
     {
+        if(dimCount != 4) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1] && i3 >= dim[2] && i4 >= dim[3]) throw new SubscriptOutOfRange();
         return array[i1];//array[i1 * dim[0] * dim[1] * dim[2] + i2 * dim[1] + i3];
     }
     T opIndexAssign(T v, int i1)
     {
+        if(dimCount != 1) throw new SyntaxError();
+        if(i1 >= dim[0]) throw new SubscriptOutOfRange();
         return array[i1] = v;
     }
     T opIndexAssign(T v, int i1, int i2)
     {
+        if(dimCount != 2) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1]) throw new SubscriptOutOfRange();
         return array[i1 * dim[0] + i2] = v;
     }
     T opIndexAssign(T v, int i1, int i2, int i3)
     {
+        if(dimCount != 3) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1] && i3 >= dim[2]) throw new SubscriptOutOfRange();
         return array[i1 * dim[0] * dim[1] + i2 * dim[1] + i3] = v;
     }
     T opIndexAssign(T v, int i1, int i2, int i3, int i4)
     {
+        if(dimCount != 4) throw new SyntaxError();
+        if(i1 >= dim[0] && i2 >= dim[1] && i3 >= dim[2] && i4 >= dim[3]) throw new SubscriptOutOfRange();
         return array[i1] = v;//array[i1 * dim[0] * dim[1] * dim[2] + i2 * dim[1] + i3] = v;
     }