PURPOSE: To obviate the need of controlling the shower quantity on the basis of the disc position of the electron shower.

CONSTITUTION: An ion implanting device is equipped with an ion beam electric current measuring element 11 which can detect each density distribution of ion beam and electron shower 27, electrostatic lens 21 for forming a focus E consisting of the concentration of the electron shower 27 at an intermediate position between the implantation surface C of an ion radiation object article 26 and the measurement surface D of the beam electric current measuring element 11, and a beam profile monitor 12 for setting the electric current density to a prescribed value or less on the basis of the density distribution obtained by the beam electric current measuring element 11. Since the radiation state on the implantation surface C of the ion radiation object article 26 can be grasped by the beam electric current measuring element 11, each density distribution of the electron shower 27 and the ion beam is allowed to accord by changing the density distribution of the electron shower 27, and the electric current density can be suppressed to a prescribed value or less.