A plurality of organic EL elements which are arranged on a display panel lowers the brightness along with a lapse of light emitting time and hence, the power consumption is increased to maintain the brightness. However, the increase of the power consumption shortens a lifetime of the organic EL elements. To overcome this drawback, a power supply circuit which drives the display panel has a function of controlling an electric power supplied to the display panel to a fixed value or less in response to a detection signal from a detection part which detects a cathode current of the organic EL elements.