A light source unit emitting a light on an optical axis includes a first light emitter to emit a light in a certain wavelength band, a second light emitter to emit a light in a wavelength band different from that of the first light emitter, a third light emitter to emit a light in a wavelength band different from those of the first and second light emitters, a lighting path through which the lights from the first, second, and third light emitters are guided to propagate on the optical axis and into which the light from the third light emitter is joined at a hindmost position in a traveling direction on the optical axis, and an optical adjuster to exert an optical effect on the light from the third light emitter and not to exert an optical effect on the light rays from the first and second light emitters.