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.
