PURPOSE: To provide a means for preventing reverse insertion, which serves to easily distinguish one side from the other of an IC memory card.

CONSTITUTION: A sandblasted member 5 is used for the face side member of an exterior case constituting the substrate 1 of an IC memory card. Sandblasting may be applied to the back side member of the exterior case. The surface treatment is not limited to sandblasting. The face and the back of the card are so treated that these can be easily judged by touch. For example, these may be formed into a corrugated shape. The face and the back are easily judged and reverse insertion is surely prevented in cooperation with the guide grooves 3, 4 for preventing reverse insertion by means of physical specification of the IC memory card.