Abstract: [The present invention provides] a light source device comprising: a light conductor which has a first light incident end surface, a second light incident end surface and a light emitting surface; a first primary light source and a second primary light source which are disposed respectively adjacent to the first light incident end surface and second light incident end surface; and a light deflecting element which has a light incident surface disposed facing the light emitting surface and a light emitting surface, wherein a directional light emitting functional part with an average inclination angle of 0.5 to 15° is formed on at least one surface of the light conductor, i.e.