A display device is provided where fluctuation of current values of a light-emitting element caused by the ambient temperature change and degradation with time is suppressed. According to the invention, a monitoring element driven with a constant current is provided. After detecting a voltage in the monitoring element, the voltage is applied to a light-emitting element. That is, the monitoring element is driven with a constant current, and a voltage in the monitoring element is applied to the light-emitting element so that the light-emitting is driven with a constant voltage. When a predetermined condition is satisfied, an extrapolation power supply circuit samples voltages of the monitoring element, obtaining a mathematical formula of a change of the sampled voltages and generating a voltage based on the mathematical formula, which is supplied to the light-emitting element.