According to one embodiment, a light source device includes a plurality of light emitting elements including at least first and second light emitting elements, lightguide, first circuit, second circuit, and controller. The lightguide includes a first surface on which light from light emitting elements is incident and a second surface through which the light exits. The first circuit connects light emitting elements in series. The second circuit can bypass each of light emitting elements. The controller turns on light emitting elements using the first circuit if light emitting elements function normally, and if one of light emitting elements functions abnormally, the controller turns on the light emitting element functioning normally using the second circuit.