<p>The objective of the present invention is to provide a technology that is able to increase the lifespan of a spark plug that generates a spark discharge and AC plasma. The plasma ignition device (20) is provided with a power control unit (510) that reduces AC power (P) after generation of AC plasma in an AC power introduction period (Sa) during which AC power (P) is continuously introduced to a spark plug (100) within a maintenance power range (Rp) within which AC plasma can be maintained.</p>
