An objective is to provide a light source device having a light emission source such as a semiconductor laser (LD), an LED and a lamp, and an optical part such as a lens and a fiber for transmitting, transferring and light-focusing, in which, by controlling the amount of sulfate ions inside the device at a low level, adhesion of ammonium sulfate to the optical part can be prevented. The light source device includes a light source for emitting light, an optical part for processing light emitted from the light source, and a housing in which the optical part is housed, or to which the optical part is mounted, and the housing is formed by machining material that includes no sulfur component, and the material is exposed on the surface thereof.