The invention discloses an auxiliary head lamp device for a car equipped with a cover which is optionally fitted to a car and is lit during driving in fog or the like. The cover of this device can be opened when a solenoid of a cover driving mechanism is energized by operating a switch disposed inside the room of the car. The solenoid releases engagement of a stopper that restricts the cover urged in the opening direction. The switch may be used also as a switch for a light source bulb. After the solenoid is energized and the opening operation of the cover starts, a current to the solenoid is automatically cut off so that over-heat or burn-out of the solenoid that would occur if the current is continuously applied thereto can be prevented.