Provided is a technique of a PDP device capable of preventing error display arising from changes in discharge characteristics in a reset period particularly due to a long-period operation. In the PDP device, a slope of a slope waveform in the reset period is changed corresponding to operation time of the PDP device. And, the slope waveform is made to have a configuration having a stepwise plurality of slopes in a predetermined reset period. For example, when the operation time becomes long, rising and falling slope waveforms of a reset waveform are configured by two steps, and a first slope thereof is made steeper than a slope before the change, and a second slope is made gentle than the slope before the change. When the operation become longer, the first slope is made further steeper and the subsequent second slope is made further gentler.