ramp 2 through the scan driving ic 52 as explained in the above description the set up waveform ramp 1 in the reset period ascends up to the reset voltage vreset with the predetermined slope whereby the discharge fails to occur greatly in the cell as well as the required wall voltage is generated in the cell during a scanning process and a slope of the set down waveform ramp 2 is adjusted slowly since the energy recovery unit 50 is operating while the set down waveform ramp 2 falls down to the reference voltage vref of the sustain pulse in the address period as the sixth switch q 6 is turned on by a control signal cs 6 the first scan voltage supplying unit 54 supplies the scan electrode 12 y with the positive scan voltage vs through the scan driving ic 52 next the eleventh switch q h is turned off by a control signal csh synchronized with the data pulse applied to the address electrode 20 x and the seventh switch q 7 is turned on by a control signal c 57 as well as the twelfth switch ql is turned on by a control signal csl hence the positive scan voltage vs supplied from the first scan voltage supplying unit 54 is lowered to the negative.