PURPOSE: To exactly discriminate forgery by storing a number of a prepaid card, for which a residual amount once goes to be 0, in a prepaid terminal.

CONSTITUTION: A used card storing means 2 is provided in the prepaid terminal and the prepaid card is read by a card reading/writing means 1. It is discriminated by a registration discriminating means 3 whether the prepaid number stored to the prepaid card in advance is stored to the used card storing means 2 or not. When the prepaid number is not registered, an arithmetic processing means 4 calculates an amount in the prepaid card and the residual amount is stored through the card reading / writing means 1 to the prepaid card. When the prepaid number is registered, the arithmetic processing means 4 discriminates that the card is forged. Then, arithmetic processing is not executed. Thus, the forged card can be prevented.