The developing cartridge includes a casing, a developing roller, and a first inclined surface. The first inclined surface is positioned at an outer surface of one end portion of the casing in the second direction. The first inclined surface is fixed to the casing and is inclined relative to the first direction. The first inclined surface is movable in the first direction relative to the photosensitive drum between a first position and a second position together with the casing and the developing roller in a state where the developing cartridge 1 is attached to a drum cartridge. In a state where the first inclined surface is at the first position, the developing roller is in contact with the photosensitive drum. In a state where the first inclined surface is at the second position, the developing roller is in separation from the photosensitive drum.