A developing unit includes a developer consumption calculator calculating consumptions of developer in zones and storing the consumption in each zone into a corresponding storage region; a consumption shift unit shifting the consumption stored in the storage region corresponding to each zone to a storage region corresponding to a zone located on a downstream side in a developer conveyance direction in response to the conveying of the developer by the circulation conveyance member; a supply amount setting unit setting a supply amount from a developer supply portion based on the consumption stored in the storage region corresponding to the zone corresponding to the developer supply position; and a developer supply controller controlling supply of the developer from the developer supply portion based on the set supply amount.