A non-contact IC system 1 is mounted within the casing of a mobile telephone 100 and it includes: an antenna coil 11; an IC module 12 for receiving power and communication information via radio waves received by the antenna coil 11; a central arithmetic processing unit 13 for controlling the entire system and controlling drive power supply to the IC module 12; a regulator 14 for providing drive power to the IC module 12; a voltage detection circuit 15 for detecting the power supplied via the antenna coil 11; a battery 16; a bus 17; and a switch 18. The central arithmetic processing unit 13 controls the drive power supply to the IC module 12 in accordance with the result of detection of power supplied via the antenna coil 11 and the communication state of the IC module 12.