There are provided 2n (n is 2 or more) light sources 21a to 21d, 2n first collective optical systems composed of ellipsoidal mirrors 21a to 21d that are arranged so as to focus light beams emitted from the respective light sources, n first light combiner optical systems that are composed of prisms 23a and 23b, each having an isosceles triangular prism shape in cross section, and are arranged so as to synthesize exiting light beams from respective corresponding two of the first collective optical systems, second collective optical systems 26a and 26b arranged so as to focus exiting light beams from the respective first light combiner optical systems, a n/2 second light combiner optical system composed of a prism 27 having an isosceles triangular prism shape in cross section and arranged so as to synthesize exiting light beams from respective corresponding two of the second collective optical systems, and a third collective optical system 35 composed of a plurality of lenses and a plurality of lens arrays and arranged so as to allow exiting light beam from the second light combiner optical system to be incident thereon. The 2n first collective optical systems each have an optical axis substantially parallel to one another.