This invention achieves bendability with a small traction force, reduced device size, and improved controllability. Provided is a joint mechanism (12a) including a tubular first member (13a) having a through-hole (17) a second member (13b) disposed at the distal end of the first member (13a) and swivelable about a swivel axis intersecting a central axis thereof a flexible, tubular guide sheath (21a, 21b) extending near the central axis of the through-hole (17) and a distal end of which is fixed to the second member (13b) a manipulation wire (22a, 22b) introduced toward the distal end of the guide sheath and a turnaround section (20a, 20b) that is provided in the second member (13b) at a position decentered from the swivel axis in the radial direction and that causes the manipulation wire (22a, 22b) introduced from the first member (13a) via the guide sheath (21a, 21b) to make a U-turn toward the first member (13a). A distal end of the manipulation wire (22a, 22b) caused to make a U-turn at the turnaround section (20a, 20b) is fixed to a position decentered in the radial direction.
