A developing apparatus having a developing sleeve (10b) for carrying developer to a developing station. The developing sleeve (10b) contains therein a magnet (10a). A magnetic member (21) is disposed closely to the developing sleeve (10b), extending along a circumference of the sleeve (10b). The magnetic member (21) cooperates with said magnet (10a) to form a magnetic brush in a gap between the sleeve (10b) and the magnetic member (21) itself. The magnetic brush is effective to prevent possible leakage of the developer to the outside of a developer container (8) at longitudinal ends of the sleeve (10b).
