PURPOSE: To prevent toner from adhering to the vicinities of both ends of a discharge wire and to prevent rupture at the time of cleaning from being caused by irregular electrification or the deterioration of an electrifying wire by making the length of an aperture part in the longitudinal direction of the discharge wire shorter than the real discharge length of the discharge wire.

CONSTITUTION: The length of the aperture part in the longitudinal direction of the discharge wire 2 is made shorter than the real discharge length of the discharge wire 2. Namely, extension parts 5 are formed by extending the ends of supporting blocks 3 and 3 disposed at both ends of a shielding case 1 on the opening side of the case 1 toward the center part side of the case 1. Therefore, the contamination of the discharge wire and the case 1 in areas, where a discharge current is increased, at both ends of the discharge wire 2 is restrained. Therefore, the discharge current is made stable over a long term and the deterioration of the discharge wire caused by abnormal discharge is prevented. In such a case, the extension parts 5 are formed by partially extending the supporting blocks 3 and 3 but the same effect is obtained by attaching a different body such as a sheet member made of proper material or a tape instead of the extension parts 5.