A load-lock apparatus has a housing to enclose a first space and to accommodate a substrate, an exhaust pipe to exhaust a gas in the first space, a first gate valve provided in the housing to openably close to separate the first space and a second space, outside the housing, and a second gate valve provided in the housing to openably close to separate the first space and a third space, outside the housing. Pressure in the third space is lower than that in the second space. A capacity changing system moves a first portion of the housing to change capacity of the housing so that the capacity when gas in the first space is exhausted through the exhaust pipe is smaller than the capacity when the substrate is conveyed from the second space to the first space through the first gate valve.