In order to enable a processing circuit to certainly detect insertion of a wrong card having a conductive line without using a plate member or a coil regulating the shape of a card storage unit, when the wrong card having the conductive line is inserted from a card insertion port, formed in one surface of a housing, into the card storage unit in the housing, and the external terminal of the card is brought into contact with a contact terminal, a radio wave radiated into the housing is induced to the conductive line. A reception circuit connected to the contact terminal receives, of signals appearing at the conductive line, a radio wave signal radiated from a clock signal source in a communication control unit located at a position spaced apart from the card storage unit and supplies the detection output of the radio wave signal to a determination circuit. The determination circuit determines insertion of the wrong card having the conductive line on the basis of the detection output. During this determination operation, a switch element is set in an open state, and the contact terminal is disconnected from the processing circuit, so that the voltage induced to the conductive line of the wrong card and the voltage induced to the external terminal of a proper card can be taken a sufficient value to determine the difference therebetween.