A drum unit comprising: a photosensitive drum having a rotational axis extending in a first direction and at least one end in the first direction; and a frame (24, 25) extending in a second direction perpendicular to the first direction and being formed with a through-hole having an inner peripheral surface; characterized by a shaft-receiving device for connecting the photosensitive drum and the frame (24, 25), the shaft-receiving device comprising: a shaft-receiving portion (92, 98, 105) into which the one end is inserted in the first direction, wherein the photosensitive drum is rotatably supported by the shaft-receiving portion (92, 98, 195), the shaft-receiving portion being inserted into the through-hole in the first direction and opposing the inner peripheral surface in the second direction, wherein the shaft-receiving portion (92, 98, 105) is fixed to the frame (24, 25); and a pressing member (96, 108) opposing the inner peripheral surface in the second direction to press the photosensitive drum toward the inner peripheral surface, the pressing member (96, 108) contacting an outer peripheral surface of the one end of the photosensitive drum, wherein the inner peripheral surface has a first straight part (63a, 63b) extending in a third direction and a second straight part (64a, 64b) extending in a fourth direction different from the third direction, the pressing member is configured to press the photosensitive drum toward a position between the first straight part (63a, 63b) and the second straight part (64a, 64b). a photosensitive drum having a rotational axis extending in a first direction and at least one end in the first direction; and a frame (24, 25) extending in a second direction perpendicular to the first direction and being formed with a through-hole having an inner peripheral surface; characterized by a shaft-receiving device for connecting the photosensitive drum and the frame (24, 25), the shaft-receiving device comprising: a shaft-receiving portion (92, 98, 105) into which the one end is inserted in the first direction, wherein the photosensitive drum is rotatably supported by the shaft-receiving portion (92, 98, 195), the shaft-receiving portion being inserted into the through-hole in the first direction and opposing the inner peripheral surface in the second direction, wherein the shaft-receiving portion (92, 98, 105) is fixed to the frame (24, 25); and a pressing member (96, 108) opposing the inner peripheral surface in the second direction to press the photosensitive drum toward the inner peripheral surface, the pressing member (96, 108) contacting an outer peripheral surface of the one end of the photosensitive drum, wherein the inner peripheral surface has a first straight part (63a, 63b) extending in a third direction and a second straight part (64a, 64b) extending in a fourth direction different from the third direction, the pressing member is configured to press the photosensitive drum toward a position between the first straight part (63a, 63b) and the second straight part (64a, 64b). a shaft-receiving portion (92, 98, 105) into which the one end is inserted in the first direction, wherein the photosensitive drum is rotatably supported by the shaft-receiving portion (92, 98, 195), the shaft-receiving portion being inserted into the through-hole in the first direction and opposing the inner peripheral surface in the second direction, wherein the shaft-receiving portion (92, 98, 105) is fixed to the frame (24, 25); and a pressing member (96, 108) opposing the inner peripheral surface in the second direction to press the photosensitive drum toward the inner peripheral surface, the pressing member (96, 108) contacting an outer peripheral surface of the one end of the photosensitive drum, wherein the inner peripheral surface has a first straight part (63a, 63b) extending in a third direction and a second straight part (64a, 64b) extending in a fourth direction different from the third direction, the pressing member is configured to press the photosensitive drum toward a position between the first straight part (63a, 63b) and the second straight part (64a, 64b).