A medical overtube (1) according to the present invention comprises a curved part (2) disposed at the distal end and subjected to a bending operation, and a bending portion (3) connected to the proximal end side of the insertion portion (3), a long insertion portion (3) connected to the proximal end side of the insertion portion (3), a proximal end portion And a linear member (4a) that penetrates through the base end portion (12) and transmits a tension applied at the base end portion (12) to bend the bending portion, wherein the insertion portion (3 ), And the radial position of the linear member (4a) in the insertion portion (3) is set to be smaller than that of the linear member (4a) in the curved portion (2) And is disposed radially inward of the position in the radial direction.湾曲部の湾曲操作性を確保しながら、細径化を図ることを目的として、本発明に係る医療用オーバーチューブ(1)は、先端に配置され湾曲操作される湾曲部(2)と、湾曲部(2)の基端側に接続される長尺の挿入部(3)と、挿入部(3)の基端側に配置される基端部(12)と、挿入部(3)を長手方向に貫通して配置され、該基端部(12)において加えられた張力を伝達して湾曲部を湾曲させる線状部材(4a)とを備え、湾曲部(2)に、挿入部(3)を貫通してきた医療用デバイスを貫通可能な複数のチャネルを有し、挿入部(3)における線状部材(4a)の径方向位置が、湾曲部(2)における線状部材(4a)の径方向位置よりも径方向内方に配置されている。
