PURPOSE: To prevent the shadow effect and perform the ion implantation at the invariably optimum angle by controlling the ion implantation angle to change the angle of a silicon wafer.

CONSTITUTION: Prior to the ion implantation, the angle of a silicon wafer is changed by a drive section 9 via a control section 14 so that the ion implantation direction becomes the random direction by the X-ray diffraction using an X-ray detector 8. The adjustment is repeated so that the angle becomes the minimum, and the optimum ion implantation direction is determined. Then, impure ions generated by an ion source 1 are implanted to the wafer of a target section 6 via an accelerator 2, a mass spectrometer 3, a neutral beam separator 4, and a beam deflecting electrode 5. The ion implantation can be performed in the random direction at the optimum angle for the minimum shadow effect.