PURPOSE: To prevent reduction in the amount of air to be sucked even when a filter is clogged by a method wherein phase of voltage impressed on an indoor fan motor is controlled so that the number of rotation of the motor can reach a setpoint corresponding to a set value of wind amount, and the controlled phase value is shifted to a limit of an allowance of change, if it is out of the allowance of change.

CONSTITUTION: A rotation number detecting circuit 31 detects a rotation number of an indoor fan motor 7M based on an output signal of a Hall element 24. Control parts 39 and 50 control phase of voltage impressed on the indoor fan motor 7M, while surveying detection results of a zero crossing detecting circuit 34 by using a phase control circuit 32 and a double-directioned thylinster 22, so that the rotation number detected by the rotation number detecting circuit 31 become the same as a setpoint. If controlled phase value is not in an allowance of change β around a reference phase value α, control parts 30 and 50 shift the controlled phase value up to a limit (=α+{β/2}). By this, air which is conditioned to have an optimum temperature can be obtained, and therefore, comfortability can be improved.