A drum supporting structure according to one aspect of the present disclosure includes a bearing. The bearing is configured to support a flange of a photosensitive drum connected to a shaft joint member that is connected to a drive shaft through which drive power is transmitted, such that the flange of the photosensitive drum is rotatable. The bearing includes an inner circumferential surface that is fitted on an outer surface of the flange, and two planes that are formed on the inner circumferential surface and that contact with the flange. The bearing supports the flange by the flange contacting with the two planes at two points due to a load applied from a peripheral device to the photosensitive drum, such that the flange is rotatable.