PURPOSE: To prevent the intrusion of a copying material and to facilitate maintenance and cleaning operation, by providing a supporting body which has an extended copying material intrusion preventing material freely detachably to the discharging aperture of a corona discharger.

CONSTITUTION: The corona discharger 8 consists of a shielding case 9, discharging wire 10, wire lock block parts 11 and 12, etc. A frame body 13 is provided with an aperture which conforms with the discharging aperture of the case 9, an insulating line 14 for preventing the intrusion of a copying material is extended at the opening part, and hook parts 16 and 17 of both sides are provided freely detachably while engaging the engagement grooves of the block parts 11 and 12. Thus, the intrusion of the copying material is prevented, and when cleaning in the shieldimg case, replacement of the wire 10, etc., are carried out easily by detaching the frame body 13.