A planar light source device includes: a plurality of point light sources, each of which emits a light; a light guide plate that includes a first surface, and a second surface perpendicular to the first surface, and that is configured to guide the emitted lights incident from the first surface to be emitted from the second surface; a bottom case including a side portion substantially parallel to the first surface; a light source substrate that includes the plurality of point light sources arranged thereon at a predetermined interval, and that is arranged at a side of the first surface; a frame that sandwiches the light source substrate and the side portion of the bottom case and holds the second surface and that includes a plurality of gaps at positions facing the point light source.