PURPOSE: To prevent the local flocculating and sticking of a magnetic developer on the surface of a magnetic sleeve and to improve the property to transport the developer to an image carrying member by roughening the surface of the magnetic sleeve to form the ruggedness thereon and making the acute angle part of the ruggedness to obture angle.

CONSTITUTION: An aluminum cylinder is used for the blank material of the magnetic sleeve 1 as this material has a good electrical conductivity and can be reduced in weight. The surface of the cylinder is randomly roughened by using #400 abrasive grains until the surface roughness attains about 5μm in 10 points average roughness. The cylinder formed with the ruggedness by the surface roughening is then immersed into a solvent (caustic soda) to dissolve respective acute angle parts 13a and to round and to make to obture angle. The local fluocculating and sticking of the developer 19 to the surface 13 of the sleeve are, therefore, prevented and the developer is smoothly transported to a developing region.