An image forming apparatus includes a photoconductive medium electrified by an electrifying apparatus to a predetermined electric potential, a plurality of color developing apparatuses which are fixed around the photoconductive medium, each color developing apparatus having a developing roller to adhere a predetermined color toner to an electrostatic latent image formed on the photoconductive medium by a laser scanning unit, and a supplying roller to supply a toner to the developing roller, a voltage supplying apparatus to apply a predetermined bias voltage to the developing roller and the supplying roller, and a controlling apparatus to control a degree and a timing of applying the bias voltages to the developing roller and the supplying roller to control a movement state of the toner between the supplying roller and the developing roller.