A technique disclosed in the present specification relates to an ion implanter capable of preventing a semiconductor substrate from being damaged by an abnormal electric discharge through a simple method. The ion implanter of this technique includes an ion irradiation unit configured to irradiate a surface of a semiconductor substrate with ions. The ion implanter also includes at least one electrode (needle electrode, annular electrode) disposed in a position in the vicinity of at least one of back and side surfaces of an end of the semiconductor substrate. The position is dischargeable to and from the semiconductor substrate. The at least one electrode (needle electrode, annular electrode) is spaced apart from the semiconductor substrate.