There is disclosed a projector which supplies air cooled by a cooling unit to an optical element group, whereby the occurrence of dew condensation is prevented. The projector includes a cooling apparatus 11 disposed in a main body 1 and functioning as the cooling unit; a sealed or substantially sealed duct 30 through which cold air cooled by a cooler 18 of the cooling apparatus 11 is circulated and supplied to an optical element group 5 to cool the optical element group; an outside air introduction port 32 and an air discharge port 33 which function as a ventilation unit for introducing outside air into this duct 30 to discharge the air from the duct 30, dampers 34 and 35 for opening and closing these ports; and a controller C functioning as a control unit for controlling the dampers 34 and 35 to execute a ventilating operation in the duct 30.