A developing apparatus for use in an electrophotographic copying machine or the like, which includes a magnet roller having in it, a main pole magnet, with one of its poles directed outwardly and interpole magnets, with their poles opposite in polarity to the one of the poles of the main pole magnet being directed outwardly so as to attract a developing material composed of toner and carrier onto the surface of the magnet roller through magnetic induction of the main pole magnet and interpole magnets, and a doctor blade for restricting the amount of attraction of the developing material onto the surface of the magnet roller. The doctor blade has a magnet member provided in it, with its pole having the same polarity as that of the outer side pole of the main pole magnet being adapted to confront the magnet roller.