Abstract: The host computer of a product manufacturer (1) is provided with a back order database (12) containing order information and back order information, a procurement order database (13) containing procurement order information and a production control database (14) containing production schedule information and delivery date information to manage information integrally, and the host computer of the product manufacturer (1) and the terminals of part makers (3) are connected by leased communication lines for information exchange. The part makers (3) are able to retrieve directly information contained in those databases (12, 13, 14) through the leased communication lines, and are able to enter directly production schedule information and delivery date information into the production control database (14) by means of a received order managing means (15).