Patent ID: 7269363

Claim:
A developing apparatus comprising: a first storage part that stores a first two-component developer which has a first toner concentration of a toner and an amount of electrification Q 1 ; a second storage part that stores a second two-component developer which has a second toner concentration of said toner higher than that of said first two-component developer, and an amount of electrification Q 2 when readjusted into the same toner concentration as that of said first two-component developer, where Q 2 =Q 1 ×A (A=0.6−1.5); a development processing part that supplies said first two-component developer to a developing roller so as to develop an electrostatic latent image on a photosensitive member; and a development control part that controls a component composition of said first two-component developer so as to keep the component composition within a prescribed range by replenishing said second two-component developer into said first two-component developer in an appropriate manner in accordance with the progress of the development process of said development processing part, wherein the second two-component developer is prepared by supplying agitation and charge to a two-component developer having a toner concentration of said toner less than or equal to that of the first two-component developer and thereafter adding said toner thereto.