A light source device includes: a light source unit provided with a plurality of laser light sources provided in an array, the laser light sources being divided into first and second laser light source groups; a first diffusion plate that diffuses light emitted by the first laser light source group and emits first diffused light; a second diffusion plate that diffuses light emitted by the second laser light source group and emits second diffused light having a diffusion angle greater than that of the first diffused light; and optical path merging members that bend the optical path of the first diffused light to merge the optical path of the first diffused light with the optical path of the second diffused light and supply third diffused light in which the first and second diffused light are mixed.