A flexible wire having a treatment portion for performing a treatment in a body cavity in the intermediate portion (53) has a (52) second end (51) and the first end (3) and (50), the outer periphery of the wire bundle section wire is bundled small diameter portion which is denudation or reduced in diameter relative to the other at least a portion of the surface (51a), and (52a), to include a small diameter portion and at least (55), to the stack unit I comprises operating wire is connected to the (5).第一端部(51)及び第二端部(52)を有し中間部(53)に体腔内で処置を行う処置部(3)を有する可撓性の線材(50)と、線材の外周面の少なくとも一部が他に対して縮径あるいは削剥された小径部(51a)、(52a)と、少なくとも小径部を含むように線材が束ねられた束部(55)と、この束部に接続された操作ワイヤ(5)とを備える。
