To prevent unauthorized use by a third person and the leakage of data inside a portable terminal when a portable telephone or the like is lost or stolen.

When an ID card 20 is present and the signal reception part 21 of the ID card 20 is reached without a radio wave fault, to the portable terminal 10, confirmation signals for indicating that it is a correct user are transmitted from the confirmation signal transmission part 22 of the ID card 20 to the confirmation signal reception part 13 of the portable terminal 10. When the transmitted confirmation signals reach the confirmation signal reception part 13 of the portable terminal 10 without the radio wave fault, it is recognized by the portable terminal 10 that a person who turns on the switch of the power switch part 11 of the portable terminal 10 is the correct user, the power of the portable terminal 10 is turned ON and the data communication of voice and the data, etc., is performed as the portable terminal.