A displacement control apparatus is used for a variable displacement compressor. The compressor is driven by an internal combustion engine. The compressor has an inclining swash plate and a piston, which is reciprocated by the swash plate. The stroke of the piston is changed in accordance with the inclination angle of the swash plate. The displacement of the compressor is changed between a minimum displacement and a maximum displacement in accordance with the stroke of the piston. The apparatus includes an actuator coupled to the swash plate. The actuator is actuated by exhaust pressure or intake pressure from the engine. A controller changes the inclination angle of the swash plate by actuating the actuator.