A light source device comprising a filament showing high electric power-to-visible light conversion efficiency is provided. The light source device of the present invention comprises a translucent gastight container, a filament disposed in the translucent gastight container, and a lead wire for supplying an electric current to the filament. The filament comprises a substrate formed from a metal material and a visible light-absorbing film covering the substrate. The visible light-absorbing film is transparent to lights of infrared region. The reflectance of the substrate for visible lights is thereby made low, and the reflectance of the substrate for infrared lights is thereby made high. Therefore, radiation of infrared lights is suppressed, and visible luminous efficiency can be enhanced.