A light source device includes a reflector that reflects light received from an arc tube toward an illumination receiving area, and a housing that houses the reflector to form a space through which cooling air for cooling the arc tube flows. The housing has three delivery ports disposed side by side as ports from each of which the cooling air is delivered into the space. A first delivery port included in the three delivery ports is located such that the center of the first delivery port is disposed substantially at a position aligned with the optical axis of the arc tube. Second and third delivery ports included in the three delivery ports are disposed in the vicinity of one and the other sides of the first delivery port, respectively, with respect to the optical axis.