PLASMA IGNITION DEVICE AND PLASMA IGNITION METHOD

An object of the present invention is to provide a technique of improving the life of a spark plug which generates spark discharge and AC plasma. A plasma ignition device 20 includes a power control section 510 which reduces AC power P after generation of AC plasma in an AC power supply period Sa during which the AC power P is continuously supplied to a spark plug 100 within a maintainable power range Rp within which the AC plasma can be maintained.