A developing unit for mounting in an electrophotographic image forming apparatus to supply toner to a photosensitive body, the developing unit comprising: a toner storage portion containing toner and comprising a toner supply member; a development portion wherein the toner supply member supplies toner from the toner storage portion to the development portion and the development portion comprising a developing roller and a supply roller for supplying the toner to the developing roller; wherein the toner storage portion and the development portion are divided by a partition wall, wherein the partition wall includes a supply opening defining a toner supply path from the toner storage portion to the development portion, and a discharge opening defining a toner discharge path from the development portion to the toner storage portion; characterized in that when the developing unit is mounted in the electrophotographic image forming apparatus, the development portion is disposed above the toner storage portion, the development portion comprises an auxiliary supply member that rotates facing the supply roller and conveys the toner supplied to the development portion through the supply opening to a region where the supply roller and the developing roller face each other, wherein when mounted in the electrophotographic image forming apparatus the auxiliary supply member is disposed downstream of the supply roller with respect to a rotation direction of the developing roller, and a center of the auxiliary supply member is located between a vertical straight line passing through a center of the developing roller and a vertical straight line passing through a center of the supply roller, and wherein the discharge opening is spaced apart from the supply opening. a toner storage portion containing toner and comprising a toner supply member; a development portion wherein the toner supply member supplies toner from the toner storage portion to the development portion and the development portion comprising a developing roller and a supply roller for supplying the toner to the developing roller; wherein the toner storage portion and the development portion are divided by a partition wall, wherein the partition wall includes a supply opening defining a toner supply path from the toner storage portion to the development portion, and a discharge opening defining a toner discharge path from the development portion to the toner storage portion; characterized in that when the developing unit is mounted in the electrophotographic image forming apparatus, the development portion is disposed above the toner storage portion, the development portion comprises an auxiliary supply member that rotates facing the supply roller and conveys the toner supplied to the development portion through the supply opening to a region where the supply roller and the developing roller face each other, wherein when mounted in the electrophotographic image forming apparatus the auxiliary supply member is disposed downstream of the supply roller with respect to a rotation direction of the developing roller, and a center of the auxiliary supply member is located between a vertical straight line passing through a center of the developing roller and a vertical straight line passing through a center of the supply roller, and wherein the discharge opening is spaced apart from the supply opening.