To facilitate work for assembling a head light by electrically connecting a noise shield to a line for connecting one end of an inductance onto a negative electrode side of an input power source, and electrically connecting the noise shield to a line for connecting two capacitors onto the negative electrode side of the input power source.

A noise shield 5 is electrically connected to a line for connecting one end of an inductance L2 onto a negative electrode side of an input power source. A point P1 for connecting one end of the inductance L2 onto the negative electrode side of the input power source is connected to the noise shield 5 via a lead wire LN3, thereby absorbing bulb noise produced during lighting a discharge lamp 4. In this case, the bulb noise via the noise shield 5 cannot be transmitted to a main circuit 3 but released toward the input power source. A filter circuit 2' comprises the inductance L1 and capacitors C1, C2, and the noise shield 5 is electrically connected to the connecting line between the capacitors C1, C2 and the negative electrode side of the input power source, thus absorbing the noise during lighting of the discharge lamp 4.