A DC power source unit 37 is provided which boosts source voltage from a power source portion 36. A lighting circuit 38 is provided which supplies DC voltage to loads, the DC voltage being obtained by stepping down output current of the DC power source circuit 37. A control circuit 39 is provided which controls the lighting circuit 38 in accordance with at least either voltage or current of LEDs 25 and controls the DC power source unit 37 so that a ratio of output voltage to voltage of the LEDs 25 becomes a preset fixed ratio.