A planar light source device (6) for a liquid crystal display device. The planar light source device includes a light source device (2) and a light guide plate (67). The light source device includes a light-emitting element (21), and an optical guiding member (20) that is hollow and has a reflective surface. The reflective surface receives light rays emitted by the light-emitting element, and guides the light rays out from a plurality of generally aligned through holes (23) defined in a front light-emitting surface (28) of the optical guiding member. The light guide plate has a light incident surface adjacent to the light source device. The planar light source device can greatly diminish possible dark regions on the light-emitting surface of the light guide plate, and provide uniform illumination for an LCD.