The semiconductor wafer processing apparatus includes a clean box having an opening, a lid for closing the opening, a door to be in contact with the lid and to detach the lid from the clean box, a first stopper adapted to move in conjunction with movement of the clean box without a change in its relative positional relationship with the clean box, and an unmoved second stopper. With this structure, it is possible to prevent the clean box moved on the semiconductor wafer processing apparatus from colliding with the apparatus, even if the clean box manufactured by molding using a reinforced plastic in accordance with a prescribed standard includes a manufacturing error in its size.