Abstract: An ion implantation apparatus includes an ion source having an arc chamber generating ions and a drawing electrode drawing ions from the arc chamber, a mass separator transporting only ions desired for implantation, an ion implantation chamber in which the material to be implanted by ions is placed, and a controller means for automatically controlling the distance between the arc chamber and the drawing electrode incrementally in accordance with a theoretical calculation using normalized perveance considering the kind of ions to be implanted, the accelerating voltage, and the ion current and current density distribution.