In order to prevent dust from sticking to the LCD panel, to prevent the LCD panel from being heated and to suitably adjust the position of the LCD panel, a duct is provided between cooling means for a light source and cooling means for a LCD panel to send cooling air from the LCD panel side to the light source side. Therefore, a light incidence/reflection plane of the LCD panel is disposed in an almost hermetically closed space and an optical path from an integrator lens to the LCD panel is formed in the almost hermetically closed space.