Provided is a joint mechanism including a tubular first member having a through-hole； a second member disposed at the distal end of the first member and swivelable about a swivel axis intersecting a central axis thereof； a flexible, tubular guide sheath extending near the central axis of the through-hole and a distal end of which is fixed to the second member； a manipulation wire introduced toward the distal end of the guide sheath； and a turnaround section that is provided in the second member at a position decentered from the swivel axis in the radial direction and that causes the manipulation wire introduced from the first member via the guide sheath to make a U-turn toward the first member. A distal end of the manipulation wire caused to make a U-turn at the turnaround section is fixed to a position decentered in the radial direction.
