A droplet generating apparatus is provided to a projector, so as to cool an optical member utilizing taking away of heat when droplets are vaporized. The droplets generated by the droplet generating apparatus are allowed to adhere directly to the optical member or an air flow is generated to transfer the droplets, so that the droplets are allowed to adhere to the optical member. Moreover, the optical member is cooled by cooling air, and after the droplets are included in the cooling air, the droplets are removed, so that a temperature of the cooling air is previously lowered.