A head up display (HUD) includes a housing having an opening, a transmission mechanism disposed in the housing, a cover connected to the transmission mechanism and a drive mechanism configured to drive the transmission mechanism. The cover is movable between a closed position wherein the cover hides the opening and an opened position wherein the cover is located within the housing by the transmission mechanism. While the cover moves from the closed position to the opened position, the cover moves to an intermediate position below the opening in a vertical way, and moves away from the intermediate position below the opening to the opened position in sequence.