To use an approval card within the limit of the paying capacity of a user and to permit a card company to securely collect price by deciding the write condition of sum data stored in a memory provided in an approval card main body.

When the approval card C is loaded on the antenna part 3 of a paying machine 1, communication is started between the paying machine 1 and the card C. When a prescribed processing operation is executed based on sum data stored in the memory M of the approval card C, the corresponding sum is subtracted and data is rewritten into new sum data. The sum stored in the memory M is a sum which is set within the range of the sum, which is stored in a user account memory 23 in the host computer 20 of a bank when the approval card C makes communication with the paying machine 1. That data of the sum which is set from the account memory of the possessor of the approved card C is moved to the account memory 24 of the card company is written into the condition.