A technique that can make a flexible production plan adaptable to circumstances of a production request-issuing side.A producible quantity calculation part performs Material Requirements Planning for obtaining a producible quantity and a possible production date, with respect to production request information that has at least one production request specifying a requested production quantity of a product, a requested production date, and a priority. If the producible quantity calculation part judges that a requested production quantity in one production request cannot be produced by the requested production date in that production request, then the producible quantity calculation part postpones the requested production date to a later date according to a plurality of methods, to obtain producible quantities and possible production dates. The producible quantity calculation part generates image data that display, in a table, the producible quantities and possible production dates obtained by the methods.