A remanufacturing method for a process cartridge includes (a) a step of separating a first unit and a second unit from each other; (b) a step of dismounting a developing roller mounted to the second unit which has been separated by the separation step; (c) a step of mounting an addition seal along an original seal having been mounted to a developing frame along a longitudinal direction of a developing roller frame to prevent leakage of developer through between the developing roller and the developing roller frame; (d) a step of refilling the developer into a developer accommodating portion of the second unit which has been separated by the separation step; (e) a step of remounting the developing roller to the second unit which has been separated by the separation step; and (f) a unit re-coupling step of recoupling the first unit and the second unit with each other.