To easily perform the management of a postpayment in the transaction device of a portable recording medium (card, etc.) which can be used in the both of a prepaid system and the postpayment system by providing specified reading means, input means, subtraction means, addition means and writing means.

A reading means reads data such as the data of the present remaining amount recorded in the ID NO. card 3 of a card 3 from the card 3 inserted into a transaction device main body 1. An input means inputs the data of transaction amount accompanying a transaction such as the purchase of an article, etc., in the transaction device main body 1. A subtraction means subtracts inputted transaction amount from the read remaining amount. When an addition means adds preliminarily fixed supplement amount to the card 3 when the subtracted amount is less than the prescribed amount. A writing means subtracts the transaction amount from the added amount and writes the data of the new obtained remaining amount in the card 3. Thus, the management burden of a postpayment processing can be reduced.