To prevent the recurrence of a problem caused by the diversion of an item (component) at which the problem has occurred and the use of a similar item.

The information of the items having the problems is stored in a problem measure state DB 140, the low-order constitution of a diversion source item is developed when a diversion part 160 performs diversion processing, whether or not there is the problem is determined by referring to the problem measure state DB 140 for the respective developed items, and an alarm is issued when there is the problem in one of the items. Also, when a design change is approved, a horizontal development support part 180 retrieves the item of a matching model group, a GT code or an item name code and the item to be a diversion destination from an item DB 130 for the item for which the design change is approved, newly registers them in the problem measure state DB 140 as relating items to be the object of horizontal development, and transmits problem information to a person in charge of the relating items by mail.