An ion implantation apparatus according to the invention includes a park electrode as a deflecting apparatus arranged at a section of a beam line from an outlet of a mass analysis magnet apparatus to a front side of a mass analysis slit for deflecting an ion beam in a predetermined direction of being deviated from a beam trajectory line by an operation of an electric field. When the ion beam does not satisfy a desired condition, a park voltage is applied to the park electrode, thereby, the ion beam is brought into an evacuated state by being deflected from the beam trajectory line. As a result, the ion beam cannot pass through the mass analysis slit, and therefore, the ion beam which does not arrive at a wafer to prevent the ion beam which does not satisfy the condition from being irradiated to the wafer.