A method of developing a latent image formed on a surface of an image carrier with toner grains, which constitute a developer together with magnetic carrier grains for supporting the toner grains, by depositing the developer on a developer carrier, which faces the image carrier and accommodates magnetic field forming mechanism, causing the developer carrier to convey the developer to a developing zone formed between the image carrier and the developer carrier, and forming, in the developing zone, a magnet brush including the magnetic carrier grains, which hold the toner grains and gather in a form of brush chains, and free toner grains to be released from the carrier grains, the brush chains of the magnetic carrier grains flow in the developing zone while forming the magnet brush, and, assuming that a potential of the image carrier is V.sub.pc and that a DC component of a potential of the developer carrier is V.sub.DC, the free toner grains, parted from the magnetic carrier grains flowing, fly at a means flight velocity of 1 m/s or below when V.sub.pc-V.sub.DC=400 V holds.