A light source device includes a laser optical system, a fluorescence optical system, and a light combiner combining first and second outgoing lights from the laser optical system and the fluorescent optical system. The laser optical system includes first laser optical sources emitting a plurality of outgoing lights respectively, the plurality of outgoing lights being blue, green, and red lights, or blue and red lights; a first dichroic mirror combining the plurality of outgoing lights from the first laser optical sources, and a diffusion plate reducing speckle noise and an uneven luminance of each of the plurality of outgoing lights. The fluorescence optical system includes a second laser light source, and a phosphor plate emitting, as the second outgoing light, a fluorescent light containing green and red lights by being excited by an outgoing light from the second laser light source. The light combiner includes a second dichroic mirror.