A display device includes an image generator configured to generate a service image to be visually recognized by an observer by outputting light for forming an image toward a reflector reflecting incident light toward the observer's eyes and superimposing the light on a scene, a receiver configured to receive the observer's operation of reducing a visibility of the image, and a controller configured to control a visibility of the service image in accordance with the operation performed on the receiver, and the controller is configured to cause the image generator to generate a warning image in a case in which the operation of reducing the visibility to a predetermined degree is performed.