A method of forming a multicolor toner image on an electrostatic latent image carrying member wherein developer containing a carrier and toner is transported to a developing region on a cylindrically shaped outer sleeve member of a developer transporting unit. Inside the sleeve there is provided at least one pair of magnets, the magnetic poles of which face the inner surface of the sleeve and are so arranged as to be rotatable, relative to each other, around the center axis of the sleeve. The amount of transported toner is regulated so that the amount of toner on the sleeve [mt], in mg/cm.sup.2, the peripheral speed of the image surface [V.sub.d ] and the peripheral speed of the sleeve member [V.sub.sl ] satisfy the following formulas:.vertline.V.sub.sl /V.sub.d .vertline..times.mt.gtoreq.0.4 mg/cm.sup.2.vertline.V.sub.sl /V.sub.3 .gtoreq.10