A process cartridge includes an image carrier, a developing device, a first casing for supporting the image carrier, and a second casing for supporting the developing device. The first casing and the second casing are freely combined in a rotatable manner as coupling pins are inserted into first insertion holes formed in the first casing and a second insertion hole formed in the second casing. An engaging means, by which the coupling pin is press-fit into the first insertion hole, and the coupling pin is kept from being press-fit into the first casing and the second casing after being pre-fit, is disposed in at least one of the first casing and the second casing, and the coupling pin.