PURPOSE: To achieve high-quality development free of irregularity by making the direction of lines of magnetic force, formed on a sleeve, different from the turning direction of a magnetic roll.

CONSTITUTION: A nonmagnetic sleeve and a multipolar magnetic roll, whose inside turns relatively, form a magnetic brush to perform development. In this case, the magnetic roller is so magnetized that the nap of toner moves in two directions different from the turning direction of the magnetic roller, thereby developing lines in every direction with the same density.