To draw out performance of an indoor heat exchanger at the time of a cooling operation at a maximum limit.

A pulse type motor driven expansion valve EV is fully opened, and a compressor 1 is started to be driven. A temperature difference Δt between an inlet and an outlet from an indoor outlet piping temperature t2 and an indoor inlet piping temperature t1 at the time of elapsing a predetermined time Δτis set to a first reference temperature difference Δto1, and a result obtained by subtracting the difference Δto1 from the difference Δt during continuously operating of the compressor 1 thereafter is set as a sensed supercooling degree SH. Then, an opening of the valve EV is decreased so that the sensed degree SH becomes a first predetermined sensed supercooling degree SH1 or more, and when the degree SC becomes the first degree SC1 or more, the opening p1s1 of the valve EV is contrarily set to a large value by a first predetermined opening Δp1s1. Accordingly, a refrigerant supercooling degree of an outlet of an indoor heat exchanger 1 is not largely assured, but substantially supercooling degree SH=0 is approached, and hence the performance of the exchanger can be achieved to a maximum limit.