The disclosed ion implantation apparatus has a vacuum chamber 11, a roller electrode 13 having a portion of an outer circumferential part on which a film 3 is wound, voltage application unit 23 for applying a voltage to the roller electrode, and a gas introduction unit having a gas supply outlet for supplying an ion implantation gas into the vacuum chamber, wherein the gas introduction unit and a gas discharge outlet are disposed so as to be opposite each other along the axial direction of the roller electrode, the roller electrode intervening therebetween.