A coupling member for an image forming apparatus cartridge includes a first end portion including an outer surface and a plurality of surfaces forming a recess extending in a direction from the outer surface toward the rotational axis. The plurality of surfaces include a first surface, a second surface opposite to the first surface, and a third surface extending between the first surface and the second surface. As viewed in a direction toward the recess and perpendicular to the rotational axis, the third surface faces toward outside of the recess, and both of the first and second surfaces are sloped with respect to a plane that is perpendicular to the rotational axis such that a distance measured along a direction of the rotational axis between the first and second surfaces decreases as a distance along the first and second surfaces from the outer surface increases.