A developing device is provided with: a developing roller for performing an electro-photography on a photosensitive body by using charged toners; a supplying roller for supplying the toners to the developing roller, the supplying roller being pushed against the developing roller so that an outer circumference of the supplying roller be deformed in a radius direction of the supplying roller; and a rotating device for rotating the supplying roller and the developing roller in directions opposite to each other at a contact portion between the supplying roller and the developing roller so that the toners be supplied from the supplying roller to the developing roller. A deformation amount in the radial direction of the supplying roller is not less than 0.5 mm, and a value of dividing an absolute value of a line speed on an outermost circumference of the supplying roller by an absolute value of a line speed on an outermost circumference of the developing roller is less than 0.7 when the line speed on the outermost circumference of the developing roller is set to not less than 70 mm/second.
