To appropriately transmit the movement of an engaging portion in a groove portion provided in a bending mechanism from the proximal end side to the distal end side, so that the bending operation can be performed smoothly, and following the shape of a living organ or the like An elongated member that can be suitably deformed is provided.An elongated member includes an operating member for curving or linearly deforming the elongated member, a guide portion formed with a groove portion, an engaging portion engageable with the groove portion , And a support portion 18 which supports the engagement portion movably relative to the guide portion, and between the guide portion and the engagement portion, there is provided a fitting in the groove portion A gap g allowing movement of the mating portion is formed.(FIG. 6A).【課題】湾曲機構が備える溝部内での係合部の可動を基端側から先端側へ好適に伝達させることができ、もって湾曲動作が円滑に行われるとともに生体器官等の形状に追従して好適に変形し得る長尺部材を提供する。【解決手段】長尺部材は、当該長尺部材１０を湾曲させ、または直線状に変形させるための操作部材と、溝部３０が形成されたガイド部１５、溝部に係合可能な係合部４０、およびガイド部に対して係合部を相対的に可動可能に支持する支持部１８を少なくとも備える湾曲機構２０を有しており、ガイド部と係合部との間には溝部内での係合部の可動を許容する隙間ｇが形成されている。【選択図】図６Ａ
