A light source device, includes: an arc tube which has a light emission portion containing a pair of electrodes disposed along an illumination axis, and a pair of sealing portions extending from both sides of the light emission portion; a reflector which has a reflection portion disposed in the vicinity of one of the sealing portions (the one sealing portion) of the arc tube for reflecting light emitted from the arc tube toward an illumination area; and a rectifying portion disposed between the light emission portion and the reflector for regulating a flow direction of cooling air and transmitting the light from the arc tube.