PURPOSE: To reliably recover a residing refrigerant by a method wherein the degree of superheat of a refrigerant on the inlet side of a condenser under a stop is detected, and when the degree of superheat is below a set value, it is decided that a liquid refrigerant resides in the condenser under a stop.

CONSTITUTION: When, during heating operation, a thermo is turned OFF in each of indoor machines B - F, a corresponding control valve 11 is closed to close the passage on the refrigerant outlet side of a condenser 10. A refrigerant flows in the condenser 10 but it does not flow out from the refrigerant outlet side, and it is easy to reside in the condenser 10. When an amount of a refrigerant residing in the condenser 10 under a stop is increased, the degree of superheat on the refrigerant inlet side of the condenser 10 is reduced to a low value and the degree of supercool of a refrigerant on the outlet side is increased and the degree of superheat is reduced to a value lower than a set value. When the degree of supercool is increased to a value higher than the set value, a device is in a normal operation state in which a refrigerant on the inlet side of the condenser 10 under a stop is an superheat gas refrigerant or in a special operation state in which the refrigerant is an supercooled liquid refrigerant, a refrigerant return means 41 is actuated, and the passage on the refrigerant outlet side of the condenser 10 under a stop is opened. As a result, a refrigerant in the condenser 10 flows, the refrigerant residing at the inside is returned to a refrigerant circulating system 14 togetherwith a flow refrigerant for recovery. This constitution enables proper recovery of a liquid refrigerant residing in the condenser under a stop.