PURPOSE: To perform efficient cooling even when high-power light is made incident by fixing a polarizing plate in a carburetor made of a transparent member and dipping the polarizing plate in a cooling medium.

CONSTITUTION: The cooling medium 7 discharged from a pump 4 reaches the carburetor 5 which is made of transparent glass and contains the polarizing plate 9 hermetically. In the carburetor 5, the cooling medium absorbs the heat of the polarizing plate 9 which rises in temperature by absorbing light and heat rays from a lamp 1 and reaches a condenser 3. The vaporized cooling medium 7 is cooled by the condenser 3 to become a condensate, which reaches the pump 4 and is sent to the carburettor 5 again. Thus, the cooling medium 7 circulates the cooling device to suppress the temperature rise of the polarizing plate 9. This constitution employs liquid cooling, so the power of a light source is strong, the cooling efficiency is high, and the device is reducible in size.