It is provided with a light source unit that can be thinner. Further, it is provided with a lighting apparatus and a notice bearing apparatus utilizing the light source unit.A light source unit 10 is configured with a plurality of LED modules 3, 3 and a constant current supplying section 2 consisting of electric components for holding constant of current supplied to the plurality of LED modules 3, 3. The plurality of LED modules 3, 3 and the electric components are aligned on a rectangular plate 11 of a module casing 1. Thus, it is possible to manufacture the light source unit 10 to be thinner. The electric components are arranged between the plurality of LED modules 3, 3. Thus, it is possible to reduce cable length installed in the light source unit 10 and to facilitate the installing works of the cable.