A touch display panel including a flat display panel and a touch sensing device disposed on the flat display panel is provided. The touch sensing device includes a plurality of the center sensing series and at least a margin sensing series corresponding to the display area of the flat display panel. Each center sensing series is formed by a plurality of center sensing electrodes serially connected. The margin sensing series disposed along the margin of the display area is formed by a plurality of margin sensing electrodes serially connected. Each of the margin sensing electrodes includes an inner portion and a rectangular outer portion. An area of the inner portion is substantially half of an area of the center sensing electrode. A parallel hemline is formed by the rectangular outer portions serially connected.