A portable electronic device includes a display panel disposed on a front side of the portable electronic device and a back-side keyboard disposed on a rear side of the portable electronic device. The back-side keyboard includes an icon layer and a touch sensing layer. The icon layer provides a plurality of icons. The touch sensing layer is utilized to sense the exact positions of fingers at the rear side of the portable electronic device. Each of the icons is triggered to realize an input operation of the icon when the icon is pressed by a finger from the rear side towards the front side of the portable electronic device. A user is allowed to use their longer fingers to perform an input operation from the rear side of the portable electronic device, for avoiding the drawback of using the thumbs to input and increasing the user experiences for input operation.