A developing cartridge for developing a latent image formed on the photosensitive member, which is detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes a cartridge frame; a developing device for developing, with toner, the latent image formed on the photosensitive member of the main assembly of the apparatus when mounted to the main assembly of the electrophotographic image forming apparatus; a driving force receptor for receiving, from the main assembly, a driving force for rotating the developing means when the cartridge is mounted to the main assembly, the driving force receptor being provided and exposed adjacent one end of the cartridge frame portion in a longitudinal direction of the developing means; a toner accommodating portion for accommodating the toner; a shutter movable between a closing position for covering a portion of the developing device exposed from the cartridge frame and an opening position for exposing the developing device; and a locking member for releasably locking the shutter at the closing position, the locking member being provided in the cartridge frame portion adjacent the one end.