Disclosed is a display device having a plurality of gate lines, a plurality of pixels connected with the plurality of gate lines and an optical sensor connected with a k-th gate line among the plurality of gate lines. A gate pulse applied to the k-th gate line includes a sensing gate pulse applied during a (k−i)-th horizontal period and a pixel driving gate pulse applied during a k-th horizontal period. The optical sensor connected with the k-th gate line outputs a sensing voltage in response to the sensing gate pulse. The pixel connected with the k-th gate line is applied with a data voltage in response to the pixel driving gate pulse.