Although the driving voltage of an organic EL element is gradually reduced (gradually decreases) as an ambient temperature increases, a supply voltage V.sub.SEG, which is supplied to a data electrode driver, is controlled to so as to be kept at a higher value than the driving voltage of the organic EL element by about 6 V as a margin value for supply source in an intermediate temperature range (e.g., from 20 to 60.degree. C.). In a high temperature range, the supply voltage V.sub.SEG is decreased, according to temperature rise, in a higher degree as the gradual decrease in the supply voltage V.sub.SEG in the intermediate temperature range.