An electrophotographic image forming apparatus for forming an image on a recording material, to which a cartridge is detachably mountable. The cartridge includes portion for accommodating a developer for developing an electrostatic latent image formed on an electrophotographic photosensitive member, a roller for developing the electrostatic latent image with the developer, an opening for supplying the developer to the developing roller from the developer accommodating portion, and a sealing member for unsealably sealing the developer supply opening. The apparatus includes a detector for detecting that amount of the developer deposited on a member to be detected is less than a predetermined level, a retractor for producing an electric signal for retracting the sealing member from a sealing position where the sealing member seals the developer supply opening, when the detector detects that amount of the developer deposited on the member to be detected is less than the predetermined level.