To reduce stain on a discharge electrode by air current and to improve the durability by guiding air into a shielding case from an air introducing means formed on the back surface of the shielding case reverse to a discharge direction.

An air introducing means K through which air is introduced into the shielding cases 30 of an electrifying charger 3 and a transfer charger 5 are constituted on the back surfaces of the cases 30 reverse to the discharge direction. A ventilating slit 30a or a ventilating hole 30b is formed in a range showing the size equal to or above the electrode width and/or the electrode length of the discharge electrode 32. The size and the shape of the slit 30a or the hole 30b are set so that the air discharged from the case 30 by the corona discharge by the electrode 32 may be sufficiently supplied. Then, air is introduced into the case 30 from the slit 30a or the hole 30b formed on the back surface of the case 30 reverse to the discharge direction by the electrode 32.