A developing device includes a developing container, a toner carrier, and a plurality of air outlet ports. The plurality of air outlet ports are formed in such part of a wall of the developing container as faces the toner carrier, along a longitudinal direction of the developing container, the air outlet ports communicating with a duct next to the developing container. The toner carrier includes a coat layer on the outer circumferential surface thereof. The coat layer is formed by dripping the toner carrier into a resin coating liquid with one end in the longitudinal direction thereof first, the one end being a lower end of during the dipping, and then lifting the toner carrier out of the resin coating liquid. The toner carrier is arranged such that the lower end of during the dipping is disposed on an upstream side with respect to an airflow direction in the duct.