For example, the reflector according to the present invention is a reflector made of glass for a projector which is composed of amorphous glass whose thermal expansion coefficient is 30 to 4510^-7/ C. and includes a reflective surface for reflecting light emitted from a light source and an opening for inserting a light source bulb or a conductor to the light source bulb, in which the opening is smoothed by heat-treating the surface thereof after opening-drilling, thus mechanical damage is removed from the processed part.