Disclosed are a display device and an operating method thereof. The display device includes an eye tracking circuit, a main display, an extended display, and an image processing circuit. By the eye tracking circuit disposed in the main display, the image processing circuit obtains a viewing position of eyes of a user. The image processing circuit divides an original image into a first partial image and a second partial image. The first partial image is adapted to be displayed on the main display, and the second partial image is adapted to be virtually displayed on an extended virtual display. The image processing circuit converts any pixel position on the extended virtual display into a corresponding pixel position on the extended display based on the viewing position, so as to convert the second partial image into a converted second partial image to be displayed on the extended display.