A display device is disclosed. The display device includes a display and a diffractive optical element (DOE). The display is used to show an image. When a user looks at the image within a first viewing angle range, he can see a first observed image, and when he looks at the image within a second viewing angle range, he can see a second observed image. The diffractive optical element is disposed in the lighting direction of the display to diffract the light constructing the first observed image to the second viewing angle range, thereby converting the first observed image into a third observed image and converting the second observed image into a fourth observed image at the same time.