An ion implantation device is equipped with a high-speed driving device which causes rotation of a disk that supports semiconductor wafers around its outer periphery. A center position of the disk is the axis of the high-speed rotation. A low-speed driving device causes relative movement of the disk in a radial direction. The ion implantation device calculates the movement speed of the low-speed driving device with reference to different spacings between wafers about the outer periphery and the distance from the center of the disk to the ion implantation position and controls the low speed scan speed so that ions are uniformly implanted into the wafers.