A display apparatus includes a photoelectric sensor disposed on an inner side of a frame and located corresponding to a corner of a pixel area of a display panel in a predetermined position. When the display apparatus is turned on, the display panel provides a light spot at a corner of a current pixel area of the display apparatus corresponding to the photoelectric sensor, and a micro-control circuit compares an electronic signal received from the photoelectric sensor with a sample value. If different, an interrupt is triggered to execute a position offsetting interrupt program to adjust the display parameter of the display apparatus, thereby moving the pixel area to adjust the relative position of the light spot and the photoelectric sensor, so that the relative position becomes identical to that when the pixel area of the display panel is in the predetermined position.