To provide an air conditioner having a proper indoor expansion valve opening.

This air conditioner has a table set with the indoor expansion valve opening associatively to an air temperature difference ΔT1 between an inlet and an outlet of an indoor heat exchanger 3 and a refrigerant temperature difference ΔT2 between the inlet and the outlet of the indoor heat exchanger 3. The air temperature difference ΔT1 and the refrigerant temperature difference ΔT2 are measured, the indoor expansion valve openings EVI(1), EVI(2) respectively corresponding to them are found on the basis of the table, one of the indoor expansion valve openings is selected to control the indoor expansion vale opening, the selected indoor expansion valve opening is changed over according to whether it is the case that the air temperature difference ΔT1 of this control result is increase or non-change to an air temperature difference ΔT1(α) of the preceding control result, or the case that a decision result is reduction, and the control is repeated. Thereby, because the indoor expansion valve opening 5 is kept proper even if connecting an outdoor machine of smaller capacity than indoor machine capacity, required ability can be exerted.