Provided is an ion implantation apparatus including: a vacuum processing chamber in which an ion implantation process for a wafer is performed; one or more load lock chambers that are used for bringing the wafer into the vacuum processing chamber and taking out the wafer from the vacuum processing chamber; an intermediate conveyance chamber that is disposed to be adjacent to both the vacuum processing chamber and the load lock chamber; a load lock chamber-intermediate conveyance chamber communication mechanism including a gate valve capable of sealing a load lock chamber-intermediate conveyance chamber communication port; and an intermediate conveyance chamber-vacuum processing chamber communication mechanism including a movable shielding plate capable of shielding a part or the whole of the intermediate conveyance chamber-vacuum processing chamber communication port.