An ion implantation method includes reciprocally scanning an ion beam, mechanically scanning a wafer in a direction perpendicular to the ion beam scanning direction, implanting ions into the wafer, and generating an ion implantation amount distribution in a wafer surface of an isotropic concentric circle shape for correcting non-uniformity in the wafer surface in other semiconductor manufacturing processes, by controlling a beam scanning speed in the ion beam scanning direction and a wafer scanning speed in the mechanical scanning direction at the same time and independently using the respective control functions defining speed correction amounts.