Patent ID: 8027623

Claim:
A developing device which houses developer having carrier and toner, and which develops a latent image formed on an image support unit, the developing device comprising: a plurality of transport members in which a screw part is formed on a spindle part, and which longitudinally transport the developer housed in the device to form a transport route; a supply member to supply a substance into the device; and a discharge port which is formed in a partition wall of the transport route formed by one of the transport members of the plurality of transport members, and is provided for discharging developer to outside when a surface of the developer transported by the one transport member exceeds a specified height, wherein the one transport member comprises, in a part thereof in a longitudinal direction, a cutaway region where the screw part is not formed, and the discharge port faces the cutaway region, and is formed such that a longitudinal length thereof is smaller than that of the cutaway region, the device further including a wall part, which protrudes toward an interior of the transport route from the partition wall where the discharge port exists, upstream of the transport route in relation to the discharge port and within a range of the cutaway region such that the developer collides with the wall part which prevents some of the developer from being discharged from the discharge port.