An object herein is to provide, with respect to a spark ignition-type internal combustion engine in which the pressure of the air-fuel mixture in the combustion chamber becomes high, an ignition device which can suppress occurrence of a creeping discharge and thus contributes to highly efficient operation of the internal combustion engine. The ignition device according to this application includes: an ignition plug having a high-voltage side electrode and a ground side electrode; a high voltage generation device that applies a voltage to the high-voltage side electrode of the ignition plug; and an extension device that extends a dielectric breakdown-reaching time period that is a time period from when the voltage is applied to the high-voltage side electrode of the ignition plug, to when a voltage between the high-voltage side electrode and the ground side electrode of the ignition plug reaches a dielectric breakdown voltage.