In a conventional IC card connector, guide walls provided on side walls of a housing comprise surfaces parallel to each other, and an interval between the guide walls is somewhat greater than a maximum width of a standard of the IC card. If the IC card having the width less than the maximum value of the standard is used, the IC card is greatly slanted due to a large amount of play, and an operation member of a detection switch cannot be operated by the IC card. In an IC card connector of the present embodiment, if the width of the IC card is small, the IC card is supported at sides by vertical surfaces, thus the movement of the IC card in the widthwise direction is regulated. If the width of the IC card is large, the IC card is supported at the side by a slope, thus the movement of the IC card is regulated. Accordingly, the arrangement provides a highly-reliable IC card connector device which ensures operation of an operation member of a detection switch by the IC card and ensures connection between contacts provided on the IC card and terminals.