PURPOSE: To obtain sharp images high in quality for a long period by using a developer incorporating a binder resin, a specified amount of fine magnetic particles, and polyolefin, and a carrier obtained by coating ferrite or steel core particles with a resin, and as additive, fine inorganic particles coated with an N-containing compound.

CONSTITUTION: The binary magnetic developer constitutes layer incorporating the binder resin, the 10-60 wt.% fine magnetic particles, and the polyolefin, and the carrier obtained by coating ferrite or steel core particles with a resin, and as the additive, the fine inorganic particles coated with the N-containing compound, thus permitting the mixing proportion of the toner and the carrier not to change for a long period, triboelectrifiability between the toner and the carrier to be sufficient, and a fog-free high-quality sharp images to be obtained for a long period.