PURPOSE: To enable to restart the titled device without giving any sense of over- cooling or over-heating to room-occupants by a method wherein, when restarting is intended, a compressor is driven at the predetermined lower rotational frequency, which is lower than the rotational frequency at its initial start.

CONSTITUTION: A computing means 21 computes the temperature deviation between the actual room temperature and the desired value of room temperature based upon the actual room temperature signal sent from a room temperature detecting means 11 and the signal sent from a room temperature setting means 17, when a temperature detecting means 20 of restart detects the restart of the titled device. A frequency setting signal generating means 22 compares the temperature deviation with the predetermined value. When the temperature deviation is smaller than the predetermined value, the signal corresponding to the minimum frequency is generated, while when equal to or larger, the signal corresponding to the intermediate frequency is generated. A rotational frequency variable type compressor 3 is driven at the minimum or intermediate rotational frequency based upon the minimum frequency setting signal or intermediate signal generated by the signal generating means 22.