PURPOSE: To reduce a user's work manhour and to quickly execute an arrangement change by executing automatically a change of the arrangement quantity for a production plan change of an item to which the arrangement is completed, in a production control system.

CONSTITUTION: In the case there is no change in a production plan of an arranged item, an arrangement calculating part 3 decides definitely the production plan quantity in a prescribed period, based on production plan information stored in a production plan storage part 1 for storing the production plan information of every item, and stores arrangement plan information required for the next arrangement containing the arrangement quantity and an arranged day, in an arrangement plan storage part 2. On the other hand, in the case the production plan is changed with respect to the arranged item, an after- change arrangement calculating part 4 executes the arrangement instead of the arrangement calculating part 3. In that case, the after-change arrangement calculating part 4 stores the arrangement plan information obtained by adding a difference between the arrangement quantity to the arranged item and the plan quantity after changing the plan to a first day of the next arrangement, in the arrangement plan storage part 2.