One embodiment of the present invention is a driving force transmission mechanism including a first member which is connected to a driving source and is moved in a circumferential direction about a predetermined axis by a driving force from the driving source, a second member which is movable in a circumferential direction about the predetermined axis and is arranged to be positioned on a movement locus in the circumferential direction of the first member, a cover member with flexibility which is arranged between the first member and the second member and comes in contact with at least the second member; and an indicator which is provided on the cover member and indicates in the cover member a change in state of a surface in contact with the second member.