A remanufacturing method for a process cartridge detachably mountable to a main assembly of an electrophotographic image forming apparatus, includes (a) a frame separating step of separating the first frame and the second frame from each other; (b) a developing blade dismounting step of dismounting, from the second frame, a developing blade which is mounted on the second frame to regulate an amount of the developer deposited on the developing roller; (c) a thin plate sheet material mounting step of mounting a thin sheet material on such a side of a longitudinal seal for providing a seal extended between the first frame and the second frame in a longitudinal direction of the second frame as is opposite from a side mounted to the second frame; (d) a developer filling step of filling the developer into the developer accommodating portion; (e) a developing blade mounting step of mounting the developing blade in a facing orientation which is opposite from a facing orientation in which the developing blade has been mounted on the second frame; and (f) a frame coupling step of coupling the separated first frame and second frame.