PURPOSE: To make it possible to appropriately carry out a coolant distribution in a space cooling and heating operation to a plurality of indoor units and to adjust the amount of a coolant only by an accumulator by using expansion valves driven based on an electric signal, and controlling an overcooling degree while taking a balance of the coolant supply to the plurality of indoor units by the expansion valve at the times of space cooling and heating operations.

CONSTITUTION: At the time of space cooling, a high pressure gas coolant from a compressor 1 is liquefied by an outdoor heat exchanger 5 and is further cooled by an accumulator heat exchanger 8. Then, the coolant is reduced of its pressure by expansion valves 7aW7c, introduced into indoor heat-exchangers 5aW5c where the coolant is vaporized. such a cycle is formed in which vaporized coolant segments pass through solenoid valves 6aW6v provided in gas side branch pipes 14aW14c, and are joined together and return to the compressor 1 via a four-way valve 2 and an accumulator 4. In this case, the overcooling degree at the outlet of the outdoor heat exchanger 3 is made constant by a temperature sensor 11 at the outlet of the outdoor heat exchanger 3 and at the same time, expansion valves 7aW7c are controlled by a controller 9, so that the temperatures of respective branch circuits are made uniform by temperature sensors 12aW12c.