An ion implantation method includes reciprocally scanning an ion beam, mechanically scanning a wafer in a direction perpendicular to a beam scanning direction, and implanting ions into the wafer. The wafer is divided into a plurality of implantation regions, a beam scanning speed in the beam scanning direction is set to be varied for each of the implantation regions, an ion implantation amount distribution for each of the implantation regions is controlled by changing and controlling the beam scanning speed, and the ion implantation amount for each of the implantation regions is controlled and a beam scanning frequency and a beam scanning amplitude in the control of the beam scanning speed for each of the implantation regions is made to be constant by setting a wafer mechanical scanning speed and controlling the wafer mechanical scanning speed for each of the implantation regions.