There is provided a developing cartridge that prevents forced erroneous mounting of the developing cartridge by a user and capable of easily recognizing the erroneous mounting by the user, and an electrophotographic image forming apparatus. When an erroneous mounting is performed, the developing cartridge is returned to a mounting start side from the vicinity of a mounting end position. Therefore, the user can easily recognize the erroneous mounting. By using a pressure member for urging the developing cartridge to an image carrier for detection of the erroneous mounting, deformation or damage of a main assembly or the developing cartridge can be suppressed.