An illumination device (700, 706) comprising: light source device (709, 710) comprising: at least one first light emitting device configured to emit first light of a first color in a first direction; a plurality of second light emitting devices configured to emit second light of a second color different from the first color in the first direction, a plurality of third light emitting devices configured to emit third light of a third color different from the first color and the second color in the first direction; a light separation element configured to separate the first light, the second light, and the third light into the first light and a fourth light including the second light and the third light; a first diffusion element provided on an optical path of the first light in a post stage of the light separation element and configured to diffuse the first light; and a second diffusion element provided on an optical path of the fourth light in the post stage of the light separation element and configured to diffuse the fourth light, wherein the number of the plurality of second light emitting devices is larger than the number of the at least one first light emitting device, wherein the plurality of second light emitting devices are substantially rotationally symmetrically provided around a center axis of a first light in a peripheral region of the at least one first light emitting device, wherein the number of the plurality of third light emitting devices is larger than the number of the at least one first light emitting device, wherein the plurality of third light emitting devices are arranged substantially rotationally symmetrically around the center axis of the first light in the peripheral region of the at least one first light emitting device, wherein the light emission efficiency of the at least one first light emitting device is higher than light emission efficiency of each of the plurality of second light emitting devices and the light emission efficiency of each of the plurality of third light emitting devices, and wherein diffusion power of the first diffusion element is larger than diffusion power of the second diffusion element. at least one first light emitting device configured to emit first light of a first color in a first direction; a plurality of second light emitting devices configured to emit second light of a second color different from the first color in the first direction, a plurality of third light emitting devices configured to emit third light of a third color different from the first color and the second color in the first direction; a light separation element configured to separate the first light, the second light, and the third light into the first light and a fourth light including the second light and the third light; a first diffusion element provided on an optical path of the first light in a post stage of the light separation element and configured to diffuse the first light; and a second diffusion element provided on an optical path of the fourth light in the post stage of the light separation element and configured to diffuse the fourth light, wherein the number of the plurality of second light emitting devices is larger than the number of the at least one first light emitting device, wherein the plurality of second light emitting devices are substantially rotationally symmetrically provided around a center axis of a first light in a peripheral region of the at least one first light emitting device, wherein the number of the plurality of third light emitting devices is larger than the number of the at least one first light emitting device, wherein the plurality of third light emitting devices are arranged substantially rotationally symmetrically around the center axis of the first light in the peripheral region of the at least one first light emitting device, wherein the light emission efficiency of the at least one first light emitting device is higher than light emission efficiency of each of the plurality of second light emitting devices and the light emission efficiency of each of the plurality of third light emitting devices, and wherein diffusion power of the first diffusion element is larger than diffusion power of the second diffusion element.