In an ion implantation apparatus, an interruption member interrupts an ion beam B in the middle of a beam line. A plasma shower device is provided at the downstream side of the interruption member in the beam line. A control unit causes the interruption member to interrupt the ion beam B during an ignition start period of the plasma shower device. The interruption member may be provided at the upstream side of at least one high-voltage electric field type electrode in the beam line. A gas supply unit may supply a source gas to the plasma shower device. The control unit may start the supply of the source gas from the gas supply unit after the ion beam B is interrupted by the interruption member.