It is an object of the present invention to provide a small and simply-structured light-source device. A light-source device according to the present invention includes a laser light source section, a stem on which the laser light source section is mounted, a cap with an opening, the cap being bonded to the stem in such a manner that the cap covers the laser light source section, a lens holder joined to an outer surface of the cap in such a manner that the lens holder extends over the opening, and a collimating lens supported by the lens holder, the collimating lens collimating a light ray emitted from the laser light source section and then passing through the opening.