The SAion is a leading-edge ion implanter developed for the upcoming generation. The SAion has extremely wide process coverage and high productivity throughout both the medium current (MC) and high current (HC) process ranges. In this paper, beam quality control method introduced for the SAion will be discussed. In order to carry out beam quality control, methods both to measure beam quality very precisely and to control beam quality very precisely must be satisfied simultaneously. These two technical elements have been developed and adopted in the SAion. A movable beam profiler has a beamangle measurement function in very high accuracy. A beam angle is measured very precisely at the wafer position. Based on the measurement, beam divergence control with extremely wide beam current coverage also can be carried out.