Image forming apparatus with plural developing devices

A developing unit (50K) is provided to store black developer usable with an image forming apparatus having an image carrier (40), the developing unit comprising: a developing unit housing (310) having a front side and a rear side; a developer storage portion (51K) provided in the developing unit housing (310) for storing black developer, the developer storage portion (51K) including an inclined bottom wall; a developing member (53K) to receive developer from the developer storage portion (51K) and form a developer image by supplying developer to the image carrier (40), when the developing unit (50K) is mounted in the image forming apparatus; a carrying portion (311K) provided underneath the developing member (53K) adapted to receive residual developer, the carrying portion (311K) including a horizontal surface portion extending horizontally from the front side of a bottom wall of the developing unit housing (310) and a front surface portion which is bent from the horizontal surface portion to extend toward the image carrier (40), when the developing unit (50K) is mounted in the image forming apparatus.