A light source apparatus includes a light source unit, a light diffusion element that is provided so as to be rotated about a predetermined rotation shaft and includes a plurality of diffusion regions which are consecutively formed around the rotation shaft, and a motor that rotates the light diffusion element so that a region on which light from the light source unit is incident in the light diffusion element is moved between the plurality of diffusion regions. The plurality of diffusion regions include a first diffusion region, and a second diffusion region which has diffusion characteristics different from diffusion characteristics of the first diffusion region and is provided so as to be adjacent to the first diffusion region.