A reflector according to the present invention can certainly reflect light emitted from a lamp in a desired direction without producing distortion in a reflection surface by specifying the distance between a projection portion and a back side end portion of the reflection surface of a reflector to be in the optimal range. The reflector, having a front side opening portion, a back side opening portion and a reflection surface, the reflector comprises a projection portion provided in an inner surface of the reflector, wherein, the projection portion is formed in an area at a 2.5 mm or more distance from a back side end portion of the reflection surface toward a back side.