A hybrid compressor system affords maximum cooling capability by making full use of an additional motor to improve the fuel consumption efficiency of a vehicle while ensuring passenger compartment cooling when the engine is stopped. The hybrid compressor system includes a compression unit for compressing a refrigerant, a motor for driving the compression unit, and disconnection means for disconnecting the drive force of a vehicle engine. In the hybrid compressor system, when the thermal load of the refrigeration cycle system lies within a predetermined range in a higher load region, the control means connects the disconnection means to allow the vehicle engine to drive the compression unit. When the thermal load of the refrigeration cycle system lies within a lower load region of the predetermined range, the control means disconnects the disconnection means to allow the motor to drive the compression unit even while the vehicle engine is running.