An ion implantation apparatus includes a beam scanning unit and a beam parallelizing unit arranged downstream thereof. The beam scanning unit has a scan origin in a central part of the scanning unit on a central axis of an incident ion beam. The beam parallelizing unit has a focal point of a parallelizing lens at the scan origin. The ion implantation apparatus is configured such that a focal position of the incident beam into the scanning unit is located upstream of the scan origin along the central axis of the incident beam. The focal position of the incident beam into the scanning unit is adjusted to be at a position upstream of the scan origin along the central axis of the incident beam such that a divergence phenomenon caused by the space charge effect in an exiting ion beam from the parallelizing unit is compensated.