PURPOSE: To enhance the ignitability with an ignition plug of a fuel direct injection type engine of an airplane, ship, car, etc., by purging the deposited carbon or uncombusted substance attached to the electrode by the use of the air.

CONSTITUTION: The body 8 of an ignition plug is equipped with a positive electrode 1 and negative electrode 2, and the power is supplied from a power supply 13 through terminals 6, 7. When the ignitability of the electrodes 1, 2 worsens, a compressed air is introduced from an air purge introducing hole 3, and this air passes a check valve 4, passage 9, and air conduits 5 to be jetted from a plurality of air jets 5b opened at the periphery of the electrodes 1, 2. The deposited carbon and/or uncombusted substance attached to the electrodes 1, 2 are purged with this air jet, which improves the ignitability of the ignition plug.