An image forming apparatus includes an image bearing drum, a developing roller,
a toner-supplying roller, and a controller. The developing roller deposits toner
to an electrostatic latent image formed on the image bearing drum. The toner-supplying
roller is spaced a distance in the range of 0.05 to 1.0 mm from the developing
roller and supplies toner to the developing roller. The controller applies a first
voltage to the developing roller and a second voltage to the toner-supplying roller.
The difference between the first voltage and the second voltage is greater than
130 volts and lower than a voltage above which electrical discharge occurs across
the developing member and the toner-supplying roller. The toner-supplying roller
has a surface with ridges and valleys formed therein, which extend in a longitudinal
direction of the toner-supplying roller. The ridges have a height in the range
of 10 to 1000 m.
