A liquid crystal display device includes an upper substrate, a lower substrate including a data line and a gate line insulated from the data line, a liquid crystal layer between the lower substrate and the upper substrate, a current sensing unit which detects a data current based on a data signal applied to the data line so as to detect a change in a liquid crystal capacitance of the liquid crystal layer, a rectifying amplifier which rectifies or amplifies the detected data current so as to generate and output a rectified signal, a pulse generator which generates a sensing pulse by comparing the rectified signal with a reference voltage, and a duty width detector which detects a duty width of the sensing pulse generated by the pulse generator where the reference voltage is set based on a voltage difference between data signals successively applied to the data line.