In the piston type variable displacement compressor of the present invention, in the crank chamber 5 in which the crank mechanism is arranged, the outlet 28A of the gas supply passage 28, for supplying refrigerant from the discharge chamber 22, is open at an upper position of the crank mechanism in the peripheral wall section of the housing. The control valve 29 is arranged in the middle of the gas supply passage 28, so that a flow rate of the refrigerant supplied into the crank chamber 5 via the gas supply passage 28 can be adjusted. Mist-like lubricant is mixed with the refrigerant. Therefore, even when the flow rate of the refrigerant is low, the crank chamber 5 can be excellently lubricated.