A commodity display position alert system includes commodity display shelves set in a selling floor space of a store, an RFID reader provided in each of the commodity display shelves, and a server as a system control unit. The RFID reader reads a commodity code from an RFID tag attached to a commodity. A server compares the commodity code of the commodity and display permission information stored in a database functioning as a shelf-rule storing unit and determines whether the read commodity code is a commodity code of a commodity that should be displayed on the commodity display shelf. When the server determines that a commodity other than the commodity that should be displayed on the commodity display shelf is displayed on the commodity display shelf, the server performs control for outputting a reporting signal for causing the PDA terminal to perform reporting operation.