A toner receiving member, which is open upward, is provided at a position
vertically below a lower end of a contact surface between a side seal
member and a developing roller. The toner receiving member can receive
and store toner which has leaked. In addition, when a developing
cartridge is removed from a main body casing and then placed on a
horizontal surface such as a desktop, a front wall, which serves as a
bottom surface of the toner receiving member, faces upward. Toner
collected in the toner receiving member may be prevented from leaking.