A system which solves the problem of the prior arts that residual quantity cannot be reflected on the inventory and proper inventory management is difficult particularly when the places to use and store the products are different and thoroughly enables processes to the ordering management and support of purchase and moreover the order acceptance management in the order accepting side from residual quantity and inventory management for a plurality of products is provided. In the inventory management and ordering system and the ordering management system, residual quantity of products which changes with use and inventory of products to always keep the products in the available condition are placed under the management, the residual quantity data of products obtained through management of residual quantity is reflected on the inventory management and the ordering is executed on the basis of the inventory management to which the management of residual quantity is reflected.