Apparatus for compensating for a threshold voltage of a driver element having gate and drain electrodes which controls current flowing in a light emitting element effective in an on and off state. A capacitor is disposed between the gate electrode and a drain electrode when the light emitting element is in the on state emits light and when the light emitting element is in the off state, applying a voltage to the gate and the source of the driver element and a threshold voltage between the gate and drain electrodes is detected and stored in the capacitor, by writing a signal voltage closer to a potential which causes the driver element to turn off than the potential supplied to the gate electrode of the driver element when detecting a threshold value, the signal voltage being superimposed on the threshold voltage without losing the threshold voltage of the driver element.