Regardless of whether specific products are individual products or element products, the specific products are managed by the same product code while element products are associated and handled as a group of products. A product selection server presents the element products by associating them with one another for each group of products. A user terminal allocates a unique purchase group number for each group of products to element products in purchase-requested product data. The product selection server receives the purchase-requested product data and indicates a price as a group of products based on the purchase group number. An order entry server searches an incorrect from the purchase-requested product data based on the purchase group number. A factory terminal and a distribution terminal issue business forms based on the purchase group number.