PURPOSE: To charge a capacitor despite the fluctuation in a voltage required by a plasma ignition plug, by connecting the capacitor in parallel with the discharge electrodes of the plasma ignition plug and coupling a charging current blocking means in series with the capacitor.

CONSTITUTION: When a first contact 4a of an interrupter 4 is opened by a cam 4c rotated synchronously with the rotary electrode 5a of a distributor 5, a high voltage is induced in the secondary winding 3b of the an ignition coil 3 and gradually raised. When the high voltage has exceeded a prescribed level, discharge is caused between the rotary electrode 5a and fixed electrode 5b of the distributor 5 to apply a high voltage between the discharge electrodes 6a, 6b of the plasma ignition plug 6. At that time, an electrical current flows through the primary winding 13a of a second ignition coil 13 as well. When a second contact 4b of the interrupter 4 is opened by the cam 4c, a high voltage is induced in the secondary winding 13b of the second ignition coil 13 to constantly charge the capacitor 11 through a diode 14.