A display device includes a first pixel group and a second pixel group. A central value of positive-side and negative-side grayscale voltages of the first pixel group is set to be a fixed value. A common voltage is adjusted to its optimal value with respect to the first pixel group. A difference between the common voltage adjusted to the optimal value with respect to the first pixel group and an optimal common voltage of the second pixel group is corrected by shifting entire positive-side and negative-side grayscale voltages of the second pixel group in a vertical direction.