A display device includes a display unit, a gaze line detection unit, and a control unit that includes a processor, and acts, when the processor executes a control program, as a gaze line concentration area detector that detects a gaze line concentration area on the screen, according to a trajectory of the gaze line on the screen detected by the gaze line detection unit, a counter that counts a number of objects displayed in the gaze line concentration area detected, and a display controller that enters an enlarged display mode in which the display object is displayed in an enlarged size, when one display object is included in the gaze line concentration area, and enters a help display mode in which help information is displayed, when no gaze line concentration area is detected, or when a plurality of display objects are included in the gaze line concentration area.