A light source device includes a first light source, a second light source and a composite dichroic mirror. The first light source is configured to emit light of a first wavelength band. The second light source is configured to emit light of a second wavelength band which is different from the first wavelength band. The composite dichroic mirror has a first area and a second area which characteristics is different from characteristics of the first area. The composite dichroic mirror reflects the light of the first wavelength band while transmitting the light of the second wavelength band. The light of the first wavelength band is radiated corresponding to the first area and the second area of the composite dichroic mirror, and the light of the second wavelength band is radiated corresponding to the first area of the composite dichroic mirror.