A developing roller of the present invention is made up of a nonmagnetic
sleeve and a magnet roller disposed in the sleeve. The magnet roller
includes a cylindrical magnet produced by molding a mixture of magnetic
powder and a high polymer, and a single rare-earth magnet block mounted on
the magnet at a position corresponding to a main magnetic pole for
development. The cylindrical magnet is magnetized such that magnetic poles
adjoining the main magnetic pole are opposite in polarity to the main
pole. The main pole and each pole adjoining it make an angle of 45.degree.
or less therebetween.
