The card connector of this invention has an erroneous insertion prevention mechanism that blocks the IC card at a predetermined blocking position when the IC card is wrongly inserted into the connector body. The erroneous insertion prevention mechanism has a blocking member retractably supported on the first side wall and an urging means to normally urge the blocking member to project inwardly from the second side wall. When the IC card is inserted in a correct orientation, the blocking member is guided by the inclined surface of the IC card to be retracted outwardly from the first side wall. When the IC card is inserted in a wrong orientation, the blocking member abuts against the front end of the IC card, blocking the further insertion of the IC card at the blocking position.