A controller for a variable displacement compressor that maintains high displacement while preventing excessive increase in discharge pressure. The controller includes a pressure sensing mechanism for detecting pressure of a suction pressure region in the compressor. A suction pressure controlling means controls the displacement of the compressor so that the pressure detected by the pressure sensing mechanism is converged to a predetermined suction pressure setting. A sensor detects pressure of a discharge pressure region in the compressor. A discharge pressure controlling means controls the displacement of the compressor so that the pressure detected by the sensor is converged to a predetermined discharge pressure setting. When the pressure detected by the sensor is greater than a threshold pressure, an ECU switches the control of the compressor from control with the suction pressure controlling means to control with the discharge pressure controlling means.