A portable electronic device (20, 30) which performs contactless communication with an external device (20, 30), the external device (20, 30) having both of a first battery (31a, 40) and a first carrier wave output device (24, 29, 41) to output carrier wave using electric power of the first battery (31a, 40), the portable electronic device (20, 30), comprising: a second battery (31a, 40); and a second carrier wave output device (24, 29, 41) which outputs carrier wave using electric power of the second battery (31a, 40), to supply electric power to the external device (20, 30); characterized in that the portable electronic device (20, 30) further comprises: a battery remaining capacity reading processor to acquire information indicating a remaining capacity of the first battery (31a, 40) from the external device (20,30); a comparing processor to compare the remaining capacity of the first battery (31a, 40) with a remaining capacity of the second battery (31a, 40); and a carrier wave switching request processor which requests switching of output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30), based on a comparison result by the comparing processor; wherein when the second carrier wave output device (24, 29, 41) outputs the carrier wave and the remaining capacity of the first battery (31a, 40) is larger than the remaining capacity of the second battery (31a, 40), the carrier wave switching request processor requests the switching of the output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30) so that the first carrier wave output device (24, 29, 41) outputs the carrier wave. a second battery (31a, 40); and a second carrier wave output device (24, 29, 41) which outputs carrier wave using electric power of the second battery (31a, 40), to supply electric power to the external device (20, 30); characterized in that the portable electronic device (20, 30) further comprises: a battery remaining capacity reading processor to acquire information indicating a remaining capacity of the first battery (31a, 40) from the external device (20,30); a comparing processor to compare the remaining capacity of the first battery (31a, 40) with a remaining capacity of the second battery (31a, 40); and a carrier wave switching request processor which requests switching of output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30), based on a comparison result by the comparing processor; wherein when the second carrier wave output device (24, 29, 41) outputs the carrier wave and the remaining capacity of the first battery (31a, 40) is larger than the remaining capacity of the second battery (31a, 40), the carrier wave switching request processor requests the switching of the output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30) so that the first carrier wave output device (24, 29, 41) outputs the carrier wave. a battery remaining capacity reading processor to acquire information indicating a remaining capacity of the first battery (31a, 40) from the external device (20,30); a comparing processor to compare the remaining capacity of the first battery (31a, 40) with a remaining capacity of the second battery (31a, 40); and a carrier wave switching request processor which requests switching of output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30), based on a comparison result by the comparing processor; wherein when the second carrier wave output device (24, 29, 41) outputs the carrier wave and the remaining capacity of the first battery (31a, 40) is larger than the remaining capacity of the second battery (31a, 40), the carrier wave switching request processor requests the switching of the output of the carrier wave from the portable electronic device (20, 30) to the external device (20, 30) so that the first carrier wave output device (24, 29, 41) outputs the carrier wave.