Disclosed is a printed circuit board, on which a holder for fixing a lamp is mounted, is disposed on an upper surface of a bottom cover, and an inverter supplying a driving voltage to the lamp is disposed on a lower surface of the bottom cover. The printed circuit board is electrically connected to the holder as a conductive pattern is embedded in the printed circuit board. The connector is directly mounted on the inverter, or it is connected to the inverter via a wire. In this case, the connector is also connected to the printed circuit board. Therefore, the connector of the inverter and the connector of the printed circuit board are electrically connected.