A dustproof cover having a reduced size in a depth direction is formed. In displaying a virtual image visible to a driver by reflecting projection light projected in front of a driver on a windshield (light-transmitting member), a dustproof cover provided in a path of the projection light to close an opening includes a recessed surface provided throughout a front and rear direction of a vehicle, and a cylindrical surface provided such that the recessed surface is continuous throughout a right and left direction of the vehicle. Curvatures of the recessed surface are configured to increase toward a front side of the vehicle, and therefore outer light entering the opening from a position above the vehicle is reflected in a direction invisible to the driver.