In order to cause effective function when a system adopting a conventional settlement card is shifted to a system adopting a settlement card of IC card type and to enable a significant contribution to proliferation of the settlement card of IC card type, when a person who has input authentication data is authenticated as a user of a card by an authentication section, transaction data read by a magnetic stripe reader and transaction authentication data read by a memory reader are transmitted to a host server from transaction terminal equipment. The host server conducts a transaction through use of the transaction data and the transaction authentication data, both being output from the transaction terminal equipment. When the transaction is conducted, a memory writer writes data into memory of the card or rewrites data recorded in the memory.