PURPOSE: To perform an immediate stopping of leakage of refrigerant from an indoor heat exchanger when the refrigerant is leaked out of the heat exchanger, to keep its casualties minimum and to enhance the safety thereof.

CONSTITUTION: A gas opening or closing valve 10 and a liquid opening or closing valve 11 are installed in a refrigerant pipe 9 across an indoor heat exchanger 8. There are provided the first to third refrigerant leakage sensors 15 to 17 for sensing leakage of refrigerant leaked from the indoor heat exchanger 8 to an outer area, and a refrigerant recoverying means for recoverying the refrigerant within a refrigerant flow passage at the indoor heat exchanger 8 into the refrigerant flow passage at the outdoor heat exchanger 5 and sealing it there by closing the liquid opening or closing valve 11 and the gas opening or closing valve 10 at a predetermined time interval when the leakage of the refrigerant is detected by these refrigerant leakage sensors 15 to 17.