A rotating part for an image forming apparatus includes a drive member for transmitting power; and a driven member that is rotated by the drive member. The drive member has a male part formed in a direction of a rotation axis, and the driven member has a female part that is formed in the direction of the rotation axis and into which the male part is inserted. The male part is a hexagonal male part whose cross section perpendicular to the rotation axis assumes a hexagonal shape. The female part is a twisted triangular female part that assumes a triangular cross sectional profile in a direction perpendicular to the rotation axis, and a triangle which forms a cross section of a base and a cross section of a top is twisted at a predetermined angle with respect to the rotation axis.