A process cartridge having an insertion construction for a connecting pin swingably supporting a developing unit where there are achieved an improvement in assembly property, a minimization of container deformation, and prevention of coming-off of the connecting pin due to a small press-fitting region. The connecting pin swingably supporting the developing unit is formed of a styrene-based resin composite, and, by injecting a terpene solvent from a cutout of a photosensitive drum unit frame to the outer periphery of the connecting pin, integral connection is effected between the photosensitive drum unit frame and the connecting pin, and further, between the photosensitive drum unit frame and a drum bearing member. Due to a press-fit portion between the connecting pin and the photosensitive drum unit frame, no terpene solvent flows to the developing unit side.