A plasma flood gun of an ion implanter is provided to lengthen a lifetime thereof by delaying a time for stacking contaminants on a surface of an insulating member. A filament is installed at a chamber in order to neutralize ion beams by emitting electrons. An insulating member(154) is arranged between the filament and the chamber in order to maintain an insulating state between the filament and the chamber. The insulating member includes a body and a head. The body is inserted into the chamber in order to be coupled with the chamber. The head is formed to maintain a constant interval between the filament and the chamber. A plurality of grooves(154a) are formed at an edge of an inner surface of the head facing the chamber. A fixing member is extended through the insulating member and the chamber in order to fix the filament to the chamber.
