PURPOSE: To enable increase of starting torque and to permit improvement of running efficiency both during high load running and low load running, by providing a starting relay and a switch to change over two capacitors for a high and a low load.

CONSTITUTION: Since, during the starting of a compressor 1, the voltage of a capacitor terminal is relatively low, a contact 5a of a starting relay 5 is motioned, capacitors 2 and 3 are connected in parallel to the auxiliary coil of the compressor 1 and therefore, starting torque is increased. Thus, even when load during the starting is high, the compressor 1 is started. Thereafter, when the number of revolutions of the compressor 1 is increased and the voltage of a capacitor terminal is increased, the contact 5a is disconnected, and the compressor is brought into a steady operation state. In this case, during coolant- heating heating operation in which a load on the compressor 1 is low, a capacitor 2 for a low load is used for operation. During cooling operation in which a load is high, with a change-over switch 4 changed over, a capacitor 3 for a high load is used for operation. This constitution enables drive of the compressor with high starting torque and besides with high operation efficiency.