A card connector defining one card-accommodating slot adapted to accommodate a thin card, such as a smart card, and another card-accommodating slot adapted to accommodate a thick card, such as an IC card. The insertion of thin cards completely into the card-accommodating slot which accommodates thick cards is prevented by a member which pivots into the thick card-accommodating slot. The member includes a cam surface adapted to be contacted by a thick card upon insertion into the thick card-accommodating slot and a groove adapted to accommodate a thin card upon insertion into the thick card-accommodating slot. The member is pivotally mounted by a shaft to a card guiding arm defining the thick card-accommodating slot.