A display device having an on-screen display (OSD) menu function is provided, which includes a touch display panel, a touch screen controller, a display circuit, and a multiplexer. The touch display panel includes a display layer and a touch layer. The touch screen controller detects the touch layer and outputs a first detection result. The display circuit displays a first image of a first image source on the display layer, and the display circuit has the OSD menu function. In a normal display mode, the multiplexer transmits the first detection result of the touch screen controller to the first image source. If the first detection result complies with a predetermined pattern, the OSD menu function of the display circuit is triggered, and the display circuit enters a screen adjustment mode, and the multiplexer transmits the first detection result of the touch screen controller to the display circuit.