In the energy saving mode, a card I/F circuit section is controlled to turn ON intermittently for a predetermined interval by using a switch. The I/F circuit section supplies electric power to an outside I/F part during the ON interval, and receives some communication data from the outside. When the communication data received by the I/F circuit section is a request for a return from the energy saving mode, a return to the ordinary mode is effected. Therefore, an I/F part, such as a non-contact IC card, requiring external electric power supply can be used as a factor of a request for a return from the energy saving mode. In addition, the energy consumption for that purpose can be reduced.