To directly feed a high-pressure refrigerant gas to an evaporator for auxiliary heating by arranging a pilot valve toward a valve seat so that a bypass pipeline can be opened/closed, and by connecting the inlet pipeline of an expansion valve to a pilot room being formed on the back surface of a valve body by the pilot valve.

To perform auxiliary heating by an evaporator 4, a bypass pipeline 5 is provided for feeding a high-pressure refrigerant gas being fed from a compressor 1 to the evaporator 4 through an outlet pipeline 31 of an expansion valve 3 without passing through a condenser 2. A valve body 20 of a bypass pipeline opening/closing valve 8 being used as a pilot valve is arranged toward a valve seat 201 from an upstream side between the bypass pipeline 5 and a high-pressure refrigerant gas pipeline 11, and is biassed in a closing direction by a compression coil spring 210 from the side of a pilot room 202 being formed on the back surface of the valve body 200. Then, when the differential pressure between the high-pressure refrigerant gas pipeline 11 and the bypass pipeline 5 becomes larger, the valve body 200 is opened, thus feeding the high-pressure refrigerant gas to the evaporator 4 for auxiliary heating.