A projector is provided to prevent an influence of incident light from a light source as well as light reflected and diffused in an inner wall of an optical system by comprising a diffusion preventing member. In a projector, a display element(60) forms an image signal by using the light irradiated from a light source. A projection lens(65) projects the image signal formed by the display element. A surface-treated diffusion preventing member(70) with a cylindrical shape is placed between the display element and the projection lens to guide the image signal from the display element to the projection lens.
