A merchandise management system comprises a shelf tag provided in man exhibit position of a product, and a portable reader/writer for changing a display content on the shelf tag. The shelf tag comprises a display section using an electronic paper, an IC tag, a control section which changes product information based on change information, and controls a displayed status on the shelf tag based on an electrical power signal and the product information, and a receiving section which receives the change information and the electrical power signal from the reader/writer via a radio communication, and outputs the received change information to the changing device, and outputs the received electrical power signal to the controlling device. The reader/writer generates the change information based on a displayed status to be changed, generates the electrical power signal for driving the shelf tag, and transmits it to the shelf tag.