to the direction of the movement of the carrying member 12 into the container 13 of the above described structure magnetic particles or a mixture of magnetic particles and non magnetic developer particles are supplied so that a base layer 16 is formed the mixture constituting the base layer 16 preferably contains 5 70 wt of non magnetic developer but may only have magnetic particles the particle diameter of the magnetic particle is 30 200 preferably 70 150 microns each of the magnetic particles may consist of a magnetic material or may consist of a magnetic material and non magnetic material the magnetic particles in the base layer 16 are formed into a magnetic brush by the magnetic field provided by the magnet 14 which brush is effective to perform a circulation which will be described in detail hereinafter a magnetic brush is also formed between the magnetic pole n1 and the magnetic particle confining member 15 which is effective to constrain the magnetic particles of the base layer 16 within the container 13 above the base layer 16 non magnetic developer particles are supplied to form a developer layer 17 so that two layers are formed generally horizontally in the container 13 the non magnetic developer supplied may contain a small amount of magnetic particles but even in that case the magnetic particle content of the developer layer 17 is smaller than that of the base layer 16 to the non magnetic developer particles silica particles for enhancing the flowability and or abrasive particles for effectively abrading the surface of the photosensitive member 3 may be added the formation of the two layers is not limited to this manner i e two materials are supplied separately but may be made for example by supplying a.