A control valve is used for a variable displacement compressor. The compressor has a crank chamber and a supply passage. The control valve includes a valve housing. A valve chamber is defined in the valve housing. A valve body is accommodated in the valve chamber for adjusting the opening size of the supply passage. A pressure sensing chamber is defined in the valve housing. A pressure sensing member separates the pressure sensing chamber into a first pressure chamber and a second pressure chamber. The pressure at a first pressure monitoring point is applied to the first pressure chamber. The pressure at a second pressure monitoring point located is applied to the second pressure chamber. The pressure sensing member moves the valve body in accordance with the pressure difference between the first pressure chamber and the second pressure chamber. The pressure sensing member is a bellows or a diaphragm, an actuator applies force to the pressure sensing member in accordance with external commands. The force is applied by the actuator corresponds to a target value of the pressure difference. The pressure sensing member moves the valve body such that the pressure difference seeks the target value.