A control valve for a variable displacement compressor for varying a discharging capacity of the compressor for compressing refrigerant led into a suction chamber and discharging the compressed refrigerant from a discharge chamber, by regulating a flow rate of the refrigerant led into a crankcase from the discharge chamber, the control valve comprising: a body having a discharge chamber communication port communicating with the discharge chamber, a crankcase communication port communicating with the crankcase, a suction chamber communication port communicating with the suction chamber, and a valve hole formed in a passage connecting the discharge chamber communication port and the crankcase communication port; a valve element for opening and closing a valve section, the valve element being arranged in such a manner as to move toward and away from the valve hole; a solenoid, provided on the body, which generates a solenoidal force with which to drive the valve element in a valve closing direction in accordance with an amount of current supplied thereto; and a spring that applies a biasing force in a valve opening direction to the valve element, the biasing force being against the solenoidal force, characterized in that control is performed such that a differential pressure between a discharge pressure (Pd) of the discharge chamber and a suction pressure (Ps) of the suction chamber is maintained at a preset differential pressure according to a value of current supplied to the solenoid, and wherein a slope of a control characteristic that is a change in the preset differential pressure relative to a change in the value of the current supplied to the solenoid is set such that the slope in a high current domain after an intermediate value of a possible range of the control current supplied to the solenoid is smaller than the slope in a low current domain before the intermediate value. a body having a discharge chamber communication port communicating with the discharge chamber, a crankcase communication port communicating with the crankcase, a suction chamber communication port communicating with the suction chamber, and a valve hole formed in a passage connecting the discharge chamber communication port and the crankcase communication port; a valve element for opening and closing a valve section, the valve element being arranged in such a manner as to move toward and away from the valve hole; a solenoid, provided on the body, which generates a solenoidal force with which to drive the valve element in a valve closing direction in accordance with an amount of current supplied thereto; and a spring that applies a biasing force in a valve opening direction to the valve element, the biasing force being against the solenoidal force, characterized in that control is performed such that a differential pressure between a discharge pressure (Pd) of the discharge chamber and a suction pressure (Ps) of the suction chamber is maintained at a preset differential pressure according to a value of current supplied to the solenoid, and wherein a slope of a control characteristic that is a change in the preset differential pressure relative to a change in the value of the current supplied to the solenoid is set such that the slope in a high current domain after an intermediate value of a possible range of the control current supplied to the solenoid is smaller than the slope in a low current domain before the intermediate value.