A control device controls an operation of an electric motor, which is rotated by an electric power supplied from a battery. The control device includes an inverter, a controller and a booster. The inverter includes switching elements. The inverter converts an electric power supplied from the battery and supplies the converted electric power to the motor. The controller is operated by the electric power, which is supplied from the battery, to control the operation of the inverter. The booster boosts the voltage, which is inputted from the battery, and the booster outputs the boosted voltage to the controller. In a case where the voltage of the electric power supplied from the battery to the controller is dropped, the electric power, which has the voltage boosted by the booster, can be inputted to the controller.