A light source device includes: a reflector having a concave reflecting surface; a lamp attached to a central portion of the reflector; and a visible-ray reflective film formed on the reflecting surface of the reflector. The visible-ray reflective film includes alternately stacked films including a first reflective film formed of ZnS and a second reflective film having a lower refractive index than that of the first reflective film. The light source device further includes an ultraviolet blocking member for blocking ultraviolet rays included in light emitted from a light-emitting portion of the lamp, and for passing visible rays included in light emitted from the light-emitting portion. The ultraviolet blocking member is disposed between the light-emitting portion of the lamp and the reflector.