PURPOSE: To continually obtain the optimum, stable operation condition in either case of one chamber operation or multiple chamber operation not less than two chambers.

CONSTITUTION: When two machines are simultaneously operated, refrigerant gas by means of a compressor 1 in an outdoor unit C is changed into a liquid refrigerant by means of a condenser 2, and each introduced to evaporators 6a, 6b from a branch point P through switching valves 3a, 3b, capillary tubes 4a, 4b disposed to a high pressure pipint at the indoor unit side and heat exchanging relationship, which mutually differ, and connecting pipes 5a, 5b at the low pressure side. The refrigerant gas is sucked to the compressor 1 from a junction point M through connecting pipes 7a, 7b at the low pressure side while the switching valve 3b is closed when one machine is operated as only an indoor unit A, and all refrigerants are circulated at the indoor unit A side. This machine can stably be operated because such constitution can prevent the excess of an overheat extent of gas sucked by means of the compressor 1 when one machine is operated.