Abstract: A mask control system for a semiconductor production photo engraving process (PEP step), comprising a controller including lot selecting means for selecting a lot from wafer lots to be withdrawn from a step preceding the PEP step, and wafer lots to be processing by the PEP step, and mask searching means for searching a mask corresponding to the lot selected by the lot selecting means; and a output unit for causing the controller to detect locations of mask corresponding to selected lots, and for designating a washing order for the mask detected by the controller when the masks are in a washing step. With the preferred embodiment of the invention, selection of a wafer lot and search of a mask are automatically performed, and washing of masks is carried out according to priority, thereby shortening the time required for the PEP.