To provide an optical semiconductor lighting device in which installation and working are simple, a position where a failure is caused can be identified easily, and repairing and exchanging can be done easily.

A bracket assembly in which a power supplying unit is built in is mounted on an upper part side of a heat sink having a fixing unit equipped, the power supplying unit is mounted on an upper part side of the heat sink having the fixing unit equipped, a plurality of radiating fins are projected from an inner face of the heat sink, and the upper face of the power supplying unit is arranged at a higher position than or the same position as the edge of an upper edge part of the heat sink. With this structure, installation and working become simple and a position where a failure is caused can be identified easily, and repairing and exchanging can be done easily, as well as reduction in size can be attained.