A developing device of the present invention includes a developing roller including
a sleeve and a magnet roller accommodated in the sleeve. The surface of the sleeve
s configured such that the center portion, including an image forming range corresponding
to the image forming range of an image carrier, in the direction of width perpendicular
to the direction of movement of the above has a higher developer conveying ability
than opposite end portions outward of the center portion. Opposite ends of the
magnetic pole of the magnet roller in the direction of width face the opposite
end portions of the sleeve.
