PURPOSE: To obtain an ion implanting device which can easily remove scattered resist which is scattered and stuck on a beam passing apparatus at the time of ion implantation.

CONSTITUTION: A gas generating means 21 capable of introducing reactive gas G for light ashing into the wafer opposing surface side of beam passing apparatuses 3, 4, 5, 6 through which an ion beam passes between an analyzing magnet 2 and immediately before a wafer 8 is provided. Also, an ultraviolet ray generating means 22 capable of radiating ultraviolet rays to the reactive gas G introduced into the beam passing apparatuses 3, 4, 5, 6 is provided. The reactive gas G brought into the excited state with radiation of ultraviolet rays is brought into reaction to a scattered resist stuck to the wafer opposing surface side of the beam passing apparatuses 3, 4, 5, 6 to easily remove it.