A card connector system that detachably supports a PC card and electrically connects the PC card to an electrical device. The system includes a temperature sensor to monitor temperature of the PC card to prevent the deleterious effect of heat generated by the PC card on the PC card itself and the electrical device. The sensor detects the surface temperature of the supported PC card and transmits the obtained temperature information to the electrical device. In this case, it is preferable that a transition board 33, electrically connected between the PC card and the electrical device, is used to transmit the temperature information.