An output of a resonant circuit 60 which electromagnetically couples with an external communications apparatus is rectified and taken out, and a resultant output voltage V is monitored by a switch control circuit 61. After the output voltage V has risen to or beyond a threshold Vth1, a switch element SW is turned on and off, and a state of the switch element SW in which the output voltage V becomes higher is determined. While holding the switch element SW in the state thus determined, a power supply switch element PSW is turned on when the output voltage V has further risen. As a result, even when a plurality of noncontact IC cards 6 overlaid with one another are brought close to the communications apparatus, the individual noncontact IC cards 6 can carry out data communication.