A process unit includes a rotatable image bearing member, a charging roller configured to come in contact with a surface of the image bearing member and configured to charge the surface, and a brush unit including (i) a brush including (i-1) a plate-shaped brush substrate and (i-2) brush bristles protruding from the brush substrate and configured to come into contact with a surface of the charging roller, (ii) a holding member configured to hold the brush substrate and regulate a position of the brush substrate, and (iii) a conduction member constituting at least part of a conduction path for applying a voltage to the brush, wherein the conduction member includes a contacting portion configured to contact the brush substrate, and is configured such that a direction in which the contacting portion applies a force to the brush substrate intersects with a thickness direction of the brush substrate.

Provided is an image forming apparatus capable of suppressing an influence of environment when printing on a print quality. The image forming apparatus includes a photosensitive member, a charging roller, and a power supply. The photosensitive member has a relative dielectric constant of 3.7 or more and 6.2 or less. The charging roller charges the photosensitive member and has a surface rotational resistance of 5.2 log or more and 6.1 log or less. The power supply applies a DC voltage to the charging roller.