It is made possible to prevent luminance falling and moire occurrence and change over between a two-dimensional image and a three-dimensional image partially. When displaying one of a three-dimensional image and a two-dimensional image on a background and displaying the other image in a window, a flag bit indicating whether the first and second electrodes overlap the window is set. Waveforms differing according to the flag bit are applied to the first and second electrodes as pulses applied to the opposed first and second electrodes of a variable polarization cell. As a result, three-dimensional image display is partially conducted in the window and two-dimensional image display is conducted in areas other than the window. Or two-dimensional image display is partially conducted in the window and three-dimensional image display is conducted in areas other than the window.