A display device is capable of sensing a user's touching or inputting by a laser pointer on a display panel, by means of arranging a photo transistor in some pixels of the display panel to sense off-current of the photo transistor according to a change in the quantity of external light. In addition, a common electrode overlapping a data line is arranged separately from a common electrode overlapping a read-out line from which a sensing signal is detected, thereby improving the sensing performance carried out simultaneously with the display driving, owing to reduced influence of noise caused by the display driving to the sensing signal.