To control the rotational speed of a delta connection three-phase motor by accurately detecting a back electromotive force.

This control device of a delta connection three-phase motor has a brushless delta connection three-phase motor 11, a drive circuit 12 for supplying power to the delta connection three-phase motor 11, a control circuit 13 for controlling the delta connection three-phase motor 11 to a specific speed according to a PWM control for controlling the conduction width of a pulse signal which is outputted from the drive circuit 12, and a detection circuit 14 that synchronizes a detection signal that is supplied from the control circuit 13 and is subjected to PWM to the back electromotive force, when the terminal voltage of a coil winding is opened to detect the back electromotive force and feeds back the detected back electromotive force to the control circuit 13. By synchronizing the detection signal to the back electromotive force generated under PWM control, the speed of the delta connection three-phase motor 11 is controlled by the detected back electromotive force.