A developing device of the present invention develops a latent image formed on an image carrier with a two-ingredient type developer made up of toner and carrier. The developing device includes a storing member for storing a fresh developer to be replenished. A conveying device conveys the fresh developer from the storing member to a case, which stores the two-ingredient type developer to be deposited on the image carrier, while fluidizing the fresh developer. An excess developer discharging portion is configured to discharge excess part of the two-ingredient type developer to the outside. The developer storing member is implemented as an at least partly flexible bag.