In a selection period for applying a selection voltage to a scanning strip, a high impedance section for placing a data strip in a high impedance state is provided after a constant current section for supplying a constant current to a data strip from a constant current circuit. An organic electroluminescent element to be used has a small voltage-dependency in luminous efficiencies. When performing grayshade display by PWM, a data strip is supplied with an amount of electric charges from the constant current circuit in the constant current section, the amount of electric charges being calculated by adding an amount of residual electric charges in pixels to an amount of electric charges corresponding to luminance required for respective gray scale levels, the amount of residual electric charges being found based on an estimated potential at the data strip at end of the high impedance section.