Provided are a plurality of semiconductor light emitting elements having different central light emission wavelengths, a multiplexer means for multiplexing lights, and a central wavelength converting means for controlling a light emission amount ratio of the plurality of semiconductor light emitting elements by the use of a wavelength conversion table in which a central wavelength of multiplexed laser light is obtained on the basis of information of a light emission amount and the central light emission wavelengths. Accordingly, the central wavelength of the multiplexed light is controlled to be a predetermined wavelength.
