Light source device and filament

Provided is a light source device comprising a filament that converts electrical power to visible light with high efficiency. The provided light source device comprises a translucent air-tight container, a filament disposed inside the translucent air-tight container, and a lead wire for providing current to the filament. The filament is provided with a base formed from a high melting- point metal material, and a visible-light reflectance reducing film for covering the base to reduce the visible light reflectance of the base. Visible light reflectance is reduced and infrared light reflectance is increased and therefore this configuration enables infrared light emission to be suppressed and visible light luminous flux efficiency to be increased.