A developing device includes: a housing which includes an opening portion open downward and in which a developer is stored in an internal storage space, the storage space being formed of a region of the internal space in which the developer is present; a sealing part that seals the opening portion and is removed to allow the developer to fall through the opening portion; a storage part that stores the developer having fallen through the opening portion; an inlet that is provided in the housing, allows the developer floating from the storage part to flow into the storage space from which the developer has fallen, and is different from the opening portion; and a collecting part that is provided on the housing and collects the developer having flowed into the storage space through the inlet.