A driving waveform is applied to a scan electrode while a sustain electrode is biased at a ground voltage such that a driving board for driving the sustain electrode may not be needed. In addition, when grouping a plurality of scan electrodes into a plurality of groups and representing grayscale values using a frame-subfield method, a sustain discharge may be stably generated during a sustain period by reducing a time gap between address and sustain periods. When a sustain pulse is applied during a sustain period between two adjacent address periods, the last voltage is set to be a low level voltage.