A light source device comprises a diffuser plate and a light source module disposed behind the diffuser plate. The light source module includes a substrate, a plurality of light emitting diodes mounted on the substrate, and a plurality of reflective layers each provided on a front surface of the plurality of light emitting diodes. When a distance between the centers of each of the plurality of light emitting diodes is referred to as a pitch, and a distance between the diffuser plate and the substrate is referred to as an optical distance, a ratio of the pitch to the optical distance satisfies the following expression: 2.5≤pitch/optical distance≤4.5.