RFID tags are attached to commodities sold in a selling floor of a store. The RFID tags have stored therein identification codes for enabling identification of the RFID tags. An RFID reader configured to read the identification codes stored in the RFID tags is attached to a commodity display shelf on which the commodities are displayed. When a display quantity of stock of the commodities displayed on the commodity display shelf changes and the display quantity of stock decreases to be equal to or smaller than a predetermined alert value, a server causes a radio access point to output a reporting signal for causing a PDA terminal to perform reporting operation. A store clerk can learn, by checking a message displayed by the PDA terminal, that the display quantity of stock of the commodities decreases and can take timing for display work for commodities.