A three-dimensional display device includes an image display portion for time-sharing a left eye image and a right eye image, and a parallax barrier for separating the left and right eye images provided from the image display portion into a direction of a left eye and a right eye of a user, respectively, by using a first and a second electrode set.A method includes applying a first driving voltage to the first electrode set during a first period, and applying a second driving voltage to the second electrode set during a second period. The second driving voltage has a level different from that of the first driving voltage.