PURPOSE: To provide a developing unit capable of drastically reducing a residual used developer at tone time of exchanging a developer, in the improvement of a two-component developing unit used for an electrophotographic device.

CONSTITUTION: The developing unit 100 is constituted to provide a developing roller 102 and plural developer stirring/carrying members 103 parallel with the developing roller 102 in a container 101 housing a one-component developer. An exhaust port 104 for discharging a used developer is provided on at least one of both end parts on the bottom part of the container 101, The exhaust port 104 is usually closed shutter and opened in such a manner that the shutter is moved at the time of exchanging the developer.