In the initializing period of each of sub-fields comprising one field, one of all-cell initializing operation and selective initializing operation is performed. The all-cell initializing operation causes initializing discharge in all the discharge cells for displaying an image. The selective initializing operation selectively causes initializing discharge only in the discharge cells subjected to sustaining discharge in the preceding sub-field. Provided in the all-cell initializing period is an abnormal charge erasing part in which application of a rectangular waveform voltage to the scan electrodes causes self-erasing discharge in the discharge cells having excessive wall voltage accumulated therein.