A light source unit comprising an optical wheel having a plurality of segment areas and including luminescent light emitting areas where at least two luminescent material layers having different characteristics are provided in a circumferential direction, a wheel motor for driving to rotate the optical wheel, an excitation light source for shining light on to the optical wheel, a light emitting light source and a collective optical system for collecting a light beam from the optical wheel and a light beam from the light emitting light source to the same optical path, wherein the excitation light source is selectively turned on to illuminate the at least two luminescent material layers having different characteristics which are disposed on the luminescent light emitting areas, and wherein the light emitting light source is turned on for a period of time during which the excitation light source does not shine the excitation light.