A driving force transmission mechanism includes a first member being arranged inside an insertion section of an insertion apparatus extending along a predetermined axis, a second member being arranged to be positioned on a movement locus in a circumferential direction of the first member. The mechanism includes a cover member as an outer coat of the insertion section. The cover member is arranged between the first member and the second member to come in contact with at least the second member. The mechanism also includes an indicator being provided on the cover member. The indicator indicates in the cover member a change in state of a surface in contact with the second member.
