A remanufacturing method is provided for a process cartridge which is detachably mountable to a main assembly of an electrophotgraphic image forming apparatus. The method includes a unit separating step of separating first and second units of the cartridge from each other, a developing roller dismounting step of dismounting a developing roller mounted to the second unit, which has been separated by the separation step, a sealing step of sealing with a sealant a connecting portion between a developer frame and a developing frame of the second unit at one longitudinal end of the frames, a developer refilling step of refilling developer into a developer accommodating portion of the second unit that has been separated by the separation step, a developing roller remounting step of remounting the developing roller to the second unit that has been separated by the separation step, and a unit re-coupling step of recoupling the first unit and the second unit with each other, by which the process cartridge is remanufactured without remounting a toner seal to the developer supply opening, which was unsealed by removing the toner seal upon the start of use of the process cartridge.