To reduce manpower and also update commodity information promptly when commodity information on the commodity tag appended to the commodity is changed.

A commodity tag 30 is a small electronic device with a built-in IC chip and provided with a display and an antenna, and transmits commodity information by wireless through the IC card writer 20 from a central commodity control server 8 or a store commodity control server 10, and stores the information in the memory of the commodity tag 30 and displays them on the display device. When the commodity information are changed, the central commodity control server 8 or the store commodity control server 10 transmits updated commodity information to the commodity tag 30 by wireless through the IC card writer 20. When the commodity tag 30 receives commodity information from outside, it compares a commodity code of received commodity information with the commodity code of the existing commodity information stored in the memory, and if both agree with each other, it updates the commodity information in the memory according to the received commodity information.