To simultaneously solve the deficiency of the safety of a credit card, and the deficiency of the convenience of conventional digital cash, and the deficiency of the anonymity and circulation of the credit card and the digital cash.

An ID is applied to electronic currency 1 having the configuration of currency or a card, and nor only the ID but also parity information for ID confirmation and a sum of money as necessary are written in an incorporated IC, and the reading/writing of data for the incorporated IC is electrically operated by a contact means or a non-contact means using electromagnetic waves or magnetism. The electronic currency 1 is used so as to be connected through a network 4 with an electronic currency server 5. Thus, the anonymity of the user of the electronic currency 1 can be secured, and also the circulation of the electronic currency 1 can be maintained.