A discharge bulb is provided with an arc tube main body in which an arc tube having a discharge light emitting portion (a hermetically sealed glass envelope) where electrodes are provided in such a manner as to face each other is enclosed in a cylindrical shroud glass tube. The discharge bulb is configured so that a light distribution pattern having a predetermined cut-off line is formed by light intercepting portions (light intercepting films) and a light distribution control reflector. A frost treatment is applied to only a light emitting area on an outer surface of the shroud glass tube which corresponds to an area along the cut-off line in the light distribution pattern.