It is an object of the present invention to provide a developing apparatus that can protect a developer holder and a layer thickness control member from damages and a developer from scattering in itself, while preventing a surplus supply of the developer to both ends on the peripheral surface of the developer holder. In a developing apparatus (DA1), at the back side of a layer thickness control member (1) is provided a back side elastic sealing member (7) coming in contact with the side edges of a both-end elastic sealing members (2) to seal the developer together with the back side elastic sealing member and the both-end elastic sealing members at both ends. The both-end elastic sealing members (2) seals the developer at both ends of a developer holder (3) thereof peripheral surface. In another developing apparatus (DA6), the width of the layer thickness control member (1) in a longitudinal direction is set wider than the width of the developer holder (3) in a longitudinal direction and both side edges (la) of the layer thickness control member (1) are positioned outside both side edges (3a) of the developer holder (3). Furthermore, the inner side edges (2a) of the sealing member (2) are positioned inside the side edges (3a) of the developer holder (3) and outside the side edges of the image area (I) of the image holder (5) or aligned to an extended lines of this side edges. <IMAGE> <IMAGE>
