To prevent the occurrence of defective draw up of developer by a developer carrier with an easy constitution and to obtain a good image by making the shaft diameter of a 1st developer stirring member larger on the downstream side in a developer carrying direction.

As for the shaft diameter of the shaft part 2a of the 1st stirring roller 2, a part corresponding to the downstream area is made larger than a part corresponding to the upstream area 1 in the developer carrying direction. Thus, the gap capacity between the 1st developer storing part 7a and the 1st stirring roller shaft part on the downstream side is made smaller than that in the upper stream side area, then, even in the case the developer capacity in the 1st developer storing part is reduced in the downstream area in the developer carrying direction, the uppermost level of the developer is controlled to become higher, because the gap for storing the developer 8 is small.