Provided is a light-source device comprising a light guide plate having a rectangular shape, a light source facing a side surface of the light guide plate, a reflective sheet having a rectangular shape facing one broad surface of the light guide plate, and a plate-shaped member provided at a distance from the one broad surface. The light source side edge of the reflective sheet is located inwards of a light source side edge of the light guide plate such that a part of the one broad surface on the light source side is formed as an exposed surface, and light leakage prevention unit filling the space between the exposed surface and the plate-shaped member is provided with a protruding portion protruding towards the light source. A reflective body is provided at a position corresponding to a clearance provided between the edge of the reflective sheet and the light-leakage prevention unit.