PURPOSE: To select the date of delivery which levels production and simultaneously, is desirable to a business office in the production of a product for which the date of delivery is short and no inventory is provided.

CONSTITUTION: A production day, a production line and production load corresponding to an order-received product are calculated by referring to a product master file 13 in which the production line, the production lead time and the production load of each product are stored by using an order receipt developing part 12. Besides, in a load assignment judging part 14, it is judged whether the assignment of load conforming to the calculated result of the order receipt developing part 12 is possible or not, and if it is possible, that assignment is executed. Then, if that assignment is impossible, all assignment possible days on which the production can be assigned within a range set beforehand holding the calculated production day between by using an assignment possible day calculating part 15. Next, all delivery possible days based on the calculated result are sent to the terminal equipment 21 of the business office by a communicating part 11.