A developing device comprises: a case having a developing opening; a cylindrical-shaped developer carry member disposed exposed in part to the developing opening, and rotatable for holding and carrying a developer; and a magnet member disposed fixed within the developer carry member and comprising two or more magnetic poles including a developing magnetic pole and a developer peel-off magnetic pole. In such portion of the case that not only is opposed to the outer peripheral surface of the developer carry member after it passes through the developing area but also corresponds to an area which extends from the developing magnetic pole in the rotation direction up to the developer peel-off magnetic pole and provides a normal direction magnetic flux density of 20 mT or less, a projecting portion where a clearance between its opposed portion and the outer peripheral surface of the developer carry member becomes narrowest is formed.