Abstract: A slant plate type refrigerant compressor, such as a wobble plate type refrigerant compressor, with a capacity or displacement adjusting mechanism is disclosed. The capacity adjusting mechanism includes a valve device having an expandable/contractable bellows responsive to crank chamber pressure and a valve element fixedly attached to one end of the bellows to directly control the closing and opening of a passageway which connects a crank chamber and suction chamber. The bellows has a first effective pressure receiving cross-sectional area responsive to crank chamber pressure. The valve element has a second effective pressure receiving cross-sectional area responsive to suction chamber pressure.