The present invention relates to a developing apparatus for developing an electrostatic image formed on an image carrier, comprising a developing container, a first developing member formed at the first chamber for conveying developer to a first developing portion, a second developing member provided with the second chamber for conveying the developer to a second developing portion and a magnetic field generating means for generating magnetic field for transferring the developer between the first developing member and the second developing member. The diaphragm is disposed in a non-contacting manner to the first developing member and the second developing member and has a restricting member for restricting entry of the developer out of an interior of the developing container to a space between the first developing member and the second developing member.