To match generated heat energy with a demand for heating when a peripheral temperature is low so as to improve heating performance by providing a flow rate varying means, by which a flow rate of fluid flowing in a heating loop is varied according to a demand, and restricting the flow of fluid flowing in a branch path bypassing a compressor.

The first branch path 1 including a compressor 4 and a steamer 5 connected to the upstream part of the compressor 4 is provided, and a pressure sensor 9 is arranged in an outlet of the compressor 4. The second branch path 2 including a condenser 6, a reservoir 7, a check valve 8, and a thermostat type first expansion device 10 in this order is arranged, and an electric stop valve 12 is arranged in the branch path 2 between a point B and the condenser 6. In addition, the third branch path 3 including a valve 13 and a differential pressure regulator 14 is arranged. The respective valves 12, 13 are controlled by means of a control module 5 on the basis of an output signal from the pressure sensor 9, while by means of the differential pressure regulator 14, a fluid flow inside the third branch path 3 is restricted, and fluid from the second branch path 2 can be surely sucked into the compressor 4.