PURPOSE: To effectively charge toner by using magnetic particles.

CONSTITUTION: The charge injecting electrode 7 of flate plate form to be disposed in proximity a sleeve 2 on the right side of a developing roller 1 provided with a magnet 3 rotating in the arrow direction is constituted by an electrode plate 8 composed of non-magnetic conductive material and a magnetic particle layer 9 bound with a binder 11 such as thermosetting resin. Then, when the magnetic toner 5 being attracted and conveyed on the sleeve 2 by the action of the magnet 3 passes the charge injecting electrode 7, magnetic lines of force M penetrate the electrode plate 8 perpendicularly owing to the action of the magnetic particles 10 and therefore the toner erects according to the magnetic lines of force M and all layers are evenly charged by receiving the same injection electric fields and are always deposited to the electrode plate 8, thus the specified amount of charging is accomplished in a short time.