An employee of a company that has concluded a commodity-sales-to-employees contract with a seller accesses a sales system using a dedicated URL. A certification sub-system certifies the employee based upon employee information registered in an employee database. A commodity management sub-system displays a commodity catalog indicating an employee price on the terminal screen of the employee when the employee accesses the sales system using the dedicated URL, and displays a commodity catalog indicating an ordinary price on the terminal screen of a general end-user customer when the end-user customer accesses the sales system using an ordinary URL. An account settlement system sells the commodities designated by a customer at the price indicated in the commodity catalog.