When positively charged ions are implanted into a target substrate, charge-up damage may occur on the target substrate. In order to suppress charge-up caused by secondary electrons emitted from the target substrate when positively charged ions are implanted, a conductive member is installed at a position facing the target substrate and electrically grounded with respect to a high frequency. Further, a field intensity generated in the target substrate may be reduced by controlling an RF power applied to the target substrate in pulse mode.