PURPOSE: To enable highly efficient operation and improve comfort, by installing discharge h air temperature detection means to a hot air discharge port of an indoor unit, and controlling the rotary sped of an indoor fan and a compressor based on data detected by said detection means.

CONSTITUTION: When the temperature tn of an indoor heat exchanger is risen, and it becomes tn ≥ to, the operation of an indoor fan starts. When a discharged hot air temperature t is t<t1,gentle wind operation is available, When the discharge hot air temperature is t1≤t<t2, weak wind operation is available. When it is t2≤t, strong wind operation is available. In this manner, the ai quantity is controlled into several stage based on a predetermined tempera ture. When the temperature of open air is relatively higher and the rotary speed of a compres sor is higher due to a differential temperature, the quantity of heat absorption from the open air will be extremely higher and it will become extremely higher than the discharged hot air temperature t2. When a predetermine temperature t3 and the discharged hot air tempera ture t become t>t2, the operation must be carried out by reducing gradually the rotary speed below a rotary speed Nf decided based on a differential temperature. At the same time when the temperature of open air is lower and the rotary speed of the compressor is low due to the differential temperature, the operation must be carried out by increasing gradually the rotary speed so that it may become t4≤t<t1.