A first ramp waveform rising from a first potential (Vi1) to a second potential (Vi2) is applied to a plurality of scan electrodes (SC) in a first half period of a setup period, and a third ramp waveform rising from a fifth potential (a ground potential) to a sixth potential (Vi5, Vi5′) is applied to a plurality of sustain electrodes (SU) in a period, which is shorter than the first half period, within the first half period. A second ramp waveform dropping from a third potential (Vi3) to a fourth potential (Vi4) is applied to the plurality of scan electrodes (SC) in the second half period following the first half period, and a fourth ramp waveform dropping from a seventh potential (Ve) to an eighth potential (Vi6, Vi6′) is applied to the plurality of sustain electrodes (SU) in a period, which is shorter than the second half period, within the second half period. Then, a peak value of the third ramp waveform and a peak value of the fourth ramp waveform are changed based on a state of a plasma display panel.