ls 1 to lsn select a low scan voltage vlow whereas if the level shifters ls 1 to lsn are supplied with the high voltage of the output signals s 1 to sn from the shift register 260 in the scan period spd then the level shifters ls 1 to lsn select a first high scan voltage vhigh 1 accordingly the level shifters ls 1 to lsn supply the selected voltages to each of the scan lines sl 1 to sln further if the level shifters ls 1 to lsn as shown in fig2 are supplied with the high voltage of the output signals s 1 to sn from the shift register 260 in the aging period apd then the entire level shifters ls 1 to lsn stepwise supply an aging voltage which is changed in an opposite direction to the odd numbered scan lines sl 1 sl 3 sln 1 and the even numbered scan lines sl 2 sl 4 sln for instance as shown in fig1 and 22 an aging voltage is changed in a sequence of vhigh 2 vmiddle vlow vmiddle and vhigh 2 in the odd numbered scan lines sl 1 sl 3 sln 1 from first to fifth steps a 1 to a 5 and an aging voltage is changed in a sequence of vlow vmiddle vhigh 2 vmiddle and vlow in the even numbered scan lines sl 2 sl 4 sln from first to fifth steps a 1 to a 5 or as shown in fig1 to 18b an aging voltage av 1 to avi which is changed from the first to the 2 i th steps is supplied accordingly in the aging period apd as the data lines are floated a voltage.