To provide an image forming apparatus which forms a high quality image by restricting, even in a low-temperature low-humidity environment, ununiform electrification due to abnormal discharge caused near the contact part of an electrifying member and a member to be electrified.

In a cylindrical brush electrifier 12 which is constructed in such a manner that an electrifying brush 22 made of semiconductive fiber comprising a mixture of a synthetic resin material and a conductive material is wrapped on the external circumferential surface of a cylindrical, conductive support 21, a screen member 23 is disposed in a gap between a photoreceptor 11 and the electrifying brush 22. The screen member 22 is disposed in contact with both of the electrifying brush 22 and the photoreceptor 11, and controls the gap distance between the electrifying brush 22 and the photoreceptor 11 by the thickness of the screen member 23, thereby preventing abnormal discharge. The screen member 23 is made of an insulating material. The thickness of the member 23 is preferably 400 μm or less. The position where it is inserted is upstream in the direction of the movement of the surface of the photoreceptor.