Abstract: A series control type automatic flash unit which is capable of achieving completely controlled flashing by controlling electrical energy supplied from a main capacitor to a discharge lamp by means of a first switching element connected in series with the discharge lamp. A series circuit of a second switching element conducted by a light control signal derived from light control means and a commutation capacitor is connected in parallel with the series circuit of the discharge lamp and the first switching element, and the commutation capacitor is charged by charging means in a predetermined polarity. This charging is performed at least prior to the state of commutation, and upon conduction of the second switching element by the light control signal, stored charges of the commutation capacitor are applied via the second switching element to the first switching element to place it in a reverse biased condition. As a consequence, the first switching element is turned OFF to stop lighting of the discharge lamp.