A light source device includes a light source, a homogenizer optical system provided with a first multi-lens array having a plurality of first lenses which light emitted from the light source enters, and a second multi-lens array having a plurality of second lenses each of which the light having been transmitted through corresponding one of the first lenses enters, and adapted to homogenize the light emitted from the light source, a light intensity control element adapted to control light intensity of the light emitted from the homogenizer optical system, a light collection optical system adapted to converge the light having been transmitted through the light intensity control element, and a diffusion element which the light converged by the light collection optical system enters.