In an active matrix EL display device, a drive mode is switched between constant voltage drive and constant current drive according to display contents. Whether an OLED is driven at constant current or driven at constant voltage is determined according to whether a driving TFT is driven in a saturation region or driven in a linear region. The separation between the saturation region and the linear region is determined according to a voltage applied to the gate of the TFT and a voltage applied to the OLED. By controlling those voltages, the constant voltage drive and the constant current drive can be separately used, thereby allowing a use in which respective advantages of the both drives are utilized.