A display device includes a display screen, an image capturing device, a calculating module, and an image adjusting module. The display screen is capable of displaying an image thereon, and includes a first side. The image capturing device captures an image of a viewer, and includes an image sensor with a second side parallel to the first side. The calculating module identifies a left eye image and a right eye image of the viewer from the image of the viewer, and calculates an angle formed between the first side of the display screen and an imaginary straight line passing through the actual left eye and right eye of the viewer. The image adjusting module rotates the image on the display screen to make the first side of the display screen parallel to the imaginary straight line passing through the actual left eye and right eye of the viewer.