A HUD apparatus is structured such that a first cover opens and closes a first opening, which is disposed on a path along which a combiner moves, and a second cover opens and closes a second opening, which is disposed in an optical path from a light-projecting portion of a light-emitting unit (second mirror) to the combiner. When the combiner is being moved from an accommodated position to a projecting position, the second cover retracts into a space between the combiner and the light-projecting portion while rotating forward, similarly to the first cover.