A display device includes a display substrate, a light-emitting device, an encapsulation layer over the display substrate and encapsulating the light-emitting device, a filling layer on the encapsulation layer, a first cover layer on the filling layer, an opposite substrate on the first cover layer, and a diffraction grating layer disposed between the first cover layer and the opposite substrate, wherein the diffraction grating layer includes a plurality of diffraction patterns spaced apart from each other by a certain distance, and the plurality of diffraction patterns protrude from the surface of the opposite substrate in a direction perpendicular to the opposite substrate, and the surface of the opposite substrate faces the display substrate.