A light source device comprising: a housing that is formed by a sheet metal with good heat dissipation and includes a floor, standing walls bent inwards from the floor and standing off the floor, and a sloped face provided in a direction orthogonal to the standing walls and bent inwards at a designated angle from the floor, having a reflecting member laid thereon; a light guide , placed on the inner side of the housing and extending in a direction orthogonal to the standing walls that is adapted to output primary light that is output towards an irradiated part, and secondary light that is output towards the sloped face and is adapted to reflect off the sloped face and to irradiate the irradiated part; wherein the floor has a rectangular shape, and the housing further includes a long-edge wall bent inwards from the floor along one of the long edges of the floor, and wherein the standing walls walls are bent inwards from the floor along short edges of the floor, and the sloped face is bent inwards from the floor along the other long edge of the floor at a designated angle with respect to the short-edge direction of the floor, the light source device being characterised in that light emitters are provided on opposite sides of the light guide in a direction orthogonal to the standing walls and placed in contact with the standing walls, and in that the housing further includes heat-sink-wings , continuous with the standing walls, bent in the long-edge direction, extending in the long-edge direction at an opposite side of the long-edge wall with respect to the sloped face, and facing the sloped face. a housing that is formed by a sheet metal with good heat dissipation and includes a floor, standing walls bent inwards from the floor and standing off the floor, and a sloped face provided in a direction orthogonal to the standing walls and bent inwards at a designated angle from the floor, having a reflecting member laid thereon; a light guide , placed on the inner side of the housing and extending in a direction orthogonal to the standing walls that is adapted to output primary light that is output towards an irradiated part, and secondary light that is output towards the sloped face and is adapted to reflect off the sloped face and to irradiate the irradiated part; wherein the floor has a rectangular shape, and the housing further includes a long-edge wall bent inwards from the floor along one of the long edges of the floor, and wherein the standing walls walls are bent inwards from the floor along short edges of the floor, and the sloped face is bent inwards from the floor along the other long edge of the floor at a designated angle with respect to the short-edge direction of the floor, the light source device being characterised in that light emitters are provided on opposite sides of the light guide in a direction orthogonal to the standing walls and placed in contact with the standing walls, and in that the housing further includes heat-sink-wings , continuous with the standing walls, bent in the long-edge direction, extending in the long-edge direction at an opposite side of the long-edge wall with respect to the sloped face, and facing the sloped face. <EOS>