The present invention relates to a device in which a control circuit and a power circuit for driving a compressor and a blower of an air conditioner can be simplified and the air conditioner is controlled by a single microcomputer. In this device, an AC power is converted into a DC power through a power circuit, and the DC power is applied to a plurality of windings of a first and possibly a second brushless motor . Position detecting signals of rotors of the brushless motors are inputted to the microcomputer, and drive signals for turning on as desired a plurality of semiconductor switches of first and second drive circuits of the drive circuits so that the brushless motors are rotated in response to said position detecting signals are generated. On-portions of the drive signals for turning on as desired a set of the semiconductor switches of the first and second drive circuits are subjected to chopping as desired, and these generated drive signals are outputted to control the first and second drive circuits, and the AC voltage obtained by converting the DC voltage is applied to the plurality of windings of the first and second brushless motors. This AC voltage is subjected to chopping as desired to rotation-control the first and second brushless motors and control the air conditioner. Disclosed is also the control of an air conditioner in which a compressor or a blower of the air conditioner is driven by an induction motor while the other is driven by a brushless motor.