A panel cooling system A has a pair of Sirocco fans 51A, 51B arranged at both sides of the radial direction of a projection lens 46, a suction duct portion 52A and an exhaust duct portion 52B. The suction duct portion 52A communicates a suction port of the undersurface of an armored case 2 with a suction side of each of the Sirocco fan 51A, 51B, and the exhaust duct portion 52B communicates an exhaust side of each of the Sirocco fans 51A, 51B and color lights R, G, B of an optical part. Thereby, a cooling air is blown to the vicinity of each light incident position of the color lights R, G, B of the optical part for approximately the same air quantity, so that the cooling of the optical part is performed