To prevent illegal use of an used prepaid card by destroying the LC resonance circuit of a prepaid card when it is forged or it shows zero frequency as a result of judgment by a judging means.

The LC resonance circuit is constituted by providing an inductance by forming a wiring pattern 12a in a specified width on the surface of the main body 11 of the prepaid card and a square wiring pattern 12b in a specified interval at the center of the wiring pattern 12a so that a capacitance is provided between the wiring patterns and connecting terminals of the wiring pattern 12a, 12b. The prepaid card becomes usable by receiving the resonance waves from the LC resonance circuit when it is used on the main device and the used card cannot be used again even if frequency information is rewritten by mechanically destroying the LC resonance circuit when it shows zero frequency.