A developing device includes a developer carrier that carries a developer to be supplied to an image carrier that forms an electrostatic latent image, a supply unit that supplies the developer containing toner and a carrier to the developer carrier by transporting the developer while agitating the developer along a circulation path formed through rotation of each of plural rotary members, and a delivery unit that receives a collected developer, which is the developer collected from the developer carrier, transports the collected developer by another rotary member different from the plural rotary members of the supply unit, and delivers the collected developer to the circulation path of the supply unit.

A developing device includes a supply member, a developing device body, and a closing member. The supply member supplies a developer to an image holding element that holds a developer image. The developing device body rotatably supports the supply member. The closing member closes a clearance formed between the developing device body and the supply member with one end of the closing member fixed to the developing device body and the other end, which is a free end, contacting the supply member. The closing member has plural grooves formed to extend from the other end toward the one end.