A control device for a three-phase motor includes a drive circuit that converts DC power supply voltage into three-phase AC voltage and supplies the three-phase AC voltage to the three-phase motor, a first voltage detection unit that detects terminal voltage of three phases of the three-phase motor, and a control unit that detects a point at which a first voltage value, which is a detection value of the terminal voltage, intersects a predetermined zero-cross determination level as a zero-cross point, and controls the drive circuit based on a detection result of the zero-cross point. The control unit corrects the first voltage value by multiplying the first voltage value by a first coefficient inversely proportional to an output duty ratio with respect to the three-phase motor in a case where the output duty ratio is equal to or less than a predetermined threshold.