A display device includes a display panel and a light guide unit. The display panel includes a plurality of display units, and the plurality of display units generates a plurality of display light beams with different wavelengths, respectively. The light guide unit receives the display light beams from the plurality of display units. The light guide unit includes a plurality of input diffraction regions which change traveling directions of the display light beams, respectively, a light guide region that guides the display light beams with the changed traveling directions, and an output diffraction region which directs the guided display light beams to a predetermined direction.