A load-lock apparatus includes a housing having a movable member, a first opening to allow a load-lock chamber to communicate with a processing chamber and a second opening, different from the first opening. The housing defines a volume of the load-lock chamber. A driving mechanism drives the movable member. A first gate valve is provided at the first opening, a second gate valve is provided at the second opening, and a pump reduces a pressure in the load-lock chamber. The driving mechanism drives the movable member, after loading an object into the load-lock chamber and before unloading the object from the load-lock chamber, to change the volume of the load-lock chamber. The driving mechanism decreases the volume of the load-lock chamber after the object is loaded into the load-lock chamber through the second gate valve and before the second gate valve is closed, and the pump reduces the pressure in the load-lock chamber after the volume of the load-lock chamber is decreased and the second gate valve is closed.