PURPOSE: To prevent external air from coming into contact with the surface of a photosensitive body, and ozone present in the shield case of a corona discharging device from flowing out along that surface, and image quality from deterioration by forming plural openings for passing the air at prescribed intervals in the shield case.

CONSTITUTION: An electrostatically charging corotron 2a and a transfer corotron 2b each composed of the shield case 4 and a discharge wire 5, and the case 4 is provided with the plural openings 6a, 6b in the lateral direction, and in the case of corotron 2a, the airs intruding from the side upstream in the rotation direction of the photosensitive drum 1 through the opening 6a and through between the case 4 and the drum 1 are exhausted through the opening 6b of the downstream side without coming into contact with the surface of the drum 1, and in the case of the corotron 2b, the air introduced through a ventilation hole 8 intrudes through the opening 6a of the upstream side and goes out of the opening 6b of the downstream side, thus permitting the external air and ozone to be prevented from contacting with the surface of the drum 1, and a defective image, such as lack of density, to be avoided.