The present invention provides a composite light source apparatus for phototherapy of skin disease, in which a light beam having the wavelength and optical power suitable for light-beam treatment is provided to a region to be treated (also called a ‘to-be-treated region’) through a light guide by using a composite light source so as to improve efficiency of phototherapy of skin diseases of the body including acne, malignant tumors and the like. According to the composite light source apparatus, uniform optical power can be provided through a combination of a plurality of light sources, the optical power can be provided through selection of light of a wavelength range that a user wants, and light from the light sources can be utilized to the maximum with increased light intensity.