To provide a developing unit capable of preventing, over a long period of time, the shaft of a supply roller from locking in position due to entry of toner and sticking of toner, by forming a bearing from a resin identical to a binder resin that is a component of toner, the bearing supporting the shaft of the supply roller on a casing so that the bearing is freely rotated, and by making the bearing porous.

The developing unit 200 includes: the casing 14 for storing toner; a developing roller 4 that develops an electrostatic latent image formed on a photoreceptor drum 2 using toner; the supply roller 15 that supplies toner in contact with the developing roller 4; and the bearing 20 that supports the shaft of the supply roller 15 on the casing 14 so that the bearing is freely rotated. The bearing 20 is formed from the resin identical to the binder resin that is the component of the toner. The bearing 20 is porous.

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