An HUD superimposes a display object, as a stereoscopic image or a planar image, on an actual scene. A display control device acquires information about a moving object and information about surrounding and estimates a relative distance between a display obstacle and the moving object. When it is determined that the display obstacle exists or can exist between the display object and the moving object, the display control device changes the display mode of the display object in accordance with the amount of change in the relative distance and notifies the HUD of the display mode.