An image projection apparatus includes an optical part disposed in a light path of an projection image; an enclosing unit to enclose the light path of the projection image and having an window for projecting the projection image onto a projection plane; and an air supply unit to supply air into an internal space of the enclosing unit enclosing the light path. Pressure of the internal space of the enclosing unit is kept at a positive pressure with respect to an external pressure of the enclosing unit during an image projection operation.