Displacement controller of variable displacement compressor

A controller for controlling the displacement of a variable displacement compressor (CP) that does not require an engine ECU to presume the load torque of the compressor and thus does not require the preparation of a load torque presumption map for each type of vehicle. The displacement controller includes a control valve (CV) arranged in the compressor to vary the displacement of the compressor in accordance with an instruction signal. A first computer (67) is connected to the control valve. The first computer provides the instruction signal to the control valve to adjust a torque (Tr) of the compressor to a target torque that is in accordance with a torque target signal (Trs).