To provide an O-band not to be twisted in locked on a cord and having a constant loop shape.

An O-band has an arched loop part 42 and a locking part 43, and the loop part 42 and the locking part 43 are connected to each other through a turning part 44. The degree of curvature of the arch of the loop part 42 is smaller than that of the locking part 43. Since the O-band has a structure in which large and small arched bodies are connected through the turning part, rigidify of the loop part 42 is improved by locking the locking part 43 as the smaller arched body on a cord in comparison with a conventional one. Therefore, twisting is reduced, and the loop shape is made constant.