A flange member securable to an electrophotographic photosensitive drum, the flange member being configured to rotate when subjected to a driving force from a shaft member that rotates when subjected to the driving force from a coupling member (70, 21) subjected to the driving force, the flange member comprising: a first cylindrical portion including a first outer circumferential surface (63a1) and a first inner circumferential surface (63a2); a second cylindrical portion disposed inside the first cylindrical portion in such a manner that a central axis of the second cylindrical portion is coaxial with the first cylindrical portion and including a second outer circumferential surface (63b1) and a second inner circumferential surface (63b2), wherein the coaxial central axis defines a central axis direction; an inwardly protruding portion protruding inwards from an inner circumference of the second cylindrical portion; a first wall (63f1) extending in the central axis direction and connecting the first cylindrical portion and the second cylindrical portion together, the first wall (63f1) being in contact with the shaft member to receive the driving force; a second wall (63f2) extending in the central axis direction and connecting the first cylindrical portion and the second cylindrical portion together, the second wall (63f2) being opposed to the first wall (63f1); and a connecting portion (63f3) connecting the first cylindrical portion and the second cylindrical portion together and connecting the first wall (63f1) and the second wall (63f2) together, wherein a groove is provided inside the first inner circumferential surface (63a2) and outside the second outer circumferential surface (63b1), wherein a recessed portion recessed outwards from an inner circumferential surface of the second cylindrical portion is formed by the first wall (63f1), the second wall (63f2), and the connecting portion (63f3), and wherein the connecting portion (63f3) is disposed adjacent to the inwardly protruding portion with respect to the recessed portion in the central axis direction. a first cylindrical portion including a first outer circumferential surface (63a1) and a first inner circumferential surface (63a2); a second cylindrical portion disposed inside the first cylindrical portion in such a manner that a central axis of the second cylindrical portion is coaxial with the first cylindrical portion and including a second outer circumferential surface (63b1) and a second inner circumferential surface (63b2), wherein the coaxial central axis defines a central axis direction; an inwardly protruding portion protruding inwards from an inner circumference of the second cylindrical portion; a first wall (63f1) extending in the central axis direction and connecting the first cylindrical portion and the second cylindrical portion together, the first wall (63f1) being in contact with the shaft member to receive the driving force; a second wall (63f2) extending in the central axis direction and connecting the first cylindrical portion and the second cylindrical portion together, the second wall (63f2) being opposed to the first wall (63f1); and a connecting portion (63f3) connecting the first cylindrical portion and the second cylindrical portion together and connecting the first wall (63f1) and the second wall (63f2) together, wherein a groove is provided inside the first inner circumferential surface (63a2) and outside the second outer circumferential surface (63b1), wherein a recessed portion recessed outwards from an inner circumferential surface of the second cylindrical portion is formed by the first wall (63f1), the second wall (63f2), and the connecting portion (63f3), and wherein the connecting portion (63f3) is disposed adjacent to the inwardly protruding portion with respect to the recessed portion in the central axis direction.