To prevent scattering of broken pieces of a reflecting mirror even if a high pressure discharge lamp with a reflector bursts. A light source device according to the present invention is a light source device 10 that has an arc tube 1 and a reflector 2, and a cover glass 4 is externally fitted and fixed to the rear of the reflector 2 at opposite ends thereof with a gap S therebetween. With such a configuration, even if the arc tube bursts to cause a crack in the reflector, the cover glass prevents scattering of the broken pieces of the reflector.