PURPOSE: To enable a sure supply of liquid phase refrigerant to an expanding means by a method wherein the refrigerant cooling capacity of a condenser or the refrigerant heating capacity of an evaporator is regulated so that the refrigerant, sent into the expanding means, becomes an objective supercooled condition.

CONSTITUTION: In cooling operation, the refrigerant cooling capacity of an outdoor heat exchanger No as a condenser C is regulated by the output regulation of an outside air fan Fo based on the detecting information of a first refrigerant condition detecting means Xo so that refrigerant Rw, sent from an outdoor heat exchanger No to an expansion valve exV, is kept in objective supercooled condition. On the other hand, in heating operation, the refrigerant heating capacity of the outdoor heat exchanger No as an evaporator E is regulated by regulating the output of the outside air fan Fo based on the detecting information of a second refrigerant condition detecting means Xi so that the refrigerant Rw, sent from the outdoor heat exchanger Ni into the expansion valve exV is kept in objective supercooled condition. According to this method, the refrigerant Rw, sent into the expansion valve exV, can be kept surely as the refrigerant Rw of liquid phase whereby the operation of the expansion valve can be pevented from becoming unstable.