A coupling pin for coupling a first frame and a second frame of a process cartridge detachably mountable relative to a main assembly of an electrophotographic image forming apparatus includes (a) a first shaft portion for being press-fitted into a first hole formed in the first frame; and (b) a second shaft portion for being press-fitted into a second hole formed in the first frame, where the second shaft portion is upstream of the first shaft portion in a direction of press-fitting of the coupling pin. The second shaft portion has an outer diameter which is larger than that of the first shaft portion. The pin further includes (c) a third shaft portion for being loosely fitted into a hole formed in the second frame with a gap between the third shaft portion and inside surface of the hole of the second shaft.