An object of the invention is to provide a variable displacement compressor which is capable of using a solenoid control valve which does not require a large solenoid force. The compressor is configured such that an electromagnetic proportional flow rate control valve is arranged in a refrigerant passage leading from a discharge chamber to a condenser, that a differential pressure regulating valve is arranged in a refrigerant passage leading from the discharge chamber to a crank chamber, and that a fixed orifice is arranged in a refrigerant passage leading from the crank chamber to a suction chamber, whereby the differential pressure regulating valve senses a differential pressure Pd, Pd generated across the electromagnetic proportional flow rate control valve, for control of pressure introduced into the crank chamber. Due to this configuration, the differential pressure regulating valve controls pressure Pc in the crank chamber such that the difference of pressure of refrigerant before and after passing through a restriction having openness set by the electromagnetic proportional flow rate control valve becomes constant, which makes the flow rate Qd of discharged refrigerant constant irrespective of changes in the engine rotational speed, etc. Since the differential pressure can be controlled by a small solenoid force, the variable displacement compressor can be made compact in size.