A developing device includes a developer carrying member for carrying a magnetic developer to form a developer image on an image bearing member; a developing device frame including a first accommodating chamber for accommodating the magnetic developer and including a second accommodating chamber, in which the developer carrying member is provided, for accommodating the magnetic developer supplied from the first accommodating chamber through a first opening; a removable sealing member for sealing the first opening; and a magnetic seal, provided between a longitudinal end portion of the developer carrying member and the developing device frame. The sealing member is removable through a second opening which is defined at least partly by the magnetic seal.