Provided are a bending structure and a joint function part, capable of stabilizing bending operation and simplifying a structure. In the bending structure, an inner coiled part 5 is located into an outer coiled part 3. The outer coiled part 3 has a plurality of gaps 3c distancing adjacent coils 3b in an axial direction, and coils 5b of the inner coiled part 5 are provided so as to correspond to the gaps 3c of the outer coiled part 3 and fit between the adjacent coils 3b of the outer coiled part 3 while being in contact with the adjacent coils 3b . A dimension P is set in a range meeting πR/4N≤P<d-πR/4N in which P is the dimension of the gap 3c of the outer coiled part 3 in the axial direction in a free state, N is the number of turns of the outer coiled part 3, R is a diameter of the outer coiled part 3, and d is a wire diameter of the wire 5a of the inner coiled part 5.
