In a gate turn-off thyristor including two separate gate electrodes, a first turn-off gate signal is applied to the first gate electrode and then a second turn-off gate signal is applied to the second gate electrode after a predetermined time has elapsed in order to improve the controllable anode current and to improve the capability against an anode-voltage rising rate. This is because the flow distribution of the anode current is unbalanced asymmetrical with respect to the structural center of the GTO and therefore the internal resistance between the cathode K and the second gate G2 is reduced, so that it is possible to increase the magnitude of the turn-off gate current near the time when the anode current drops sharply or at the end of the GTO switching off operation.
