ROM type RFID chips are produced while data (production numbers) assigned by a user are set in the ROM type RFID chips respectively. A header and an EDC are added and embedded to each data to thereby form an ID format. In the ID format, an application data field may be divided into a user number field and a serial number field in order to verify uniqueness of the data assigned by the user. Or the application data field may be entirely used for the set data assigned by the user in order to verify uniqueness of the numbers assigned by the user. Accordingly, production numbers can be set in chips on the basis of the data assigned by the user. As a result, verification for checking whether each product is genuine can be dispensed with, so that the cost of communication can be reduced.