A remanufacturing method for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes (a) a unit separating step of separating the first and second units from each other by removing a pair of connecting members for connecting them; (b) a developing roller dismounting step of dismounting the developing roller from the second unit having been thus separated; (c) a second end seal mounting step of mounting a second end seal in contact with or adjacent to an outside of a first end seal which is provided at each of one and the other longitudinal ends of the developing roller; (d) a developer refilling step; (e) a developing roller remounting step; (f) a unit re-coupling step; by which the process cartridge is remanufactured without mounting a toner seal to the developer supply opening having been unsealed by removing a toner seal when the process cartridge has been used.