The spiral unit comprises a tubular body having a helical fin on its outer circumferential surface, a tubular body provided along the longitudinal axis and having a proximal and a distal distal proximal to the tubular body, the outer circumference of which is along the longitudinal axis The distal side is smaller in diameter toward the longitudinal axis than the proximal portion and the distal portion has a diameter reduction force within a range slidable in the direction around the axis of the longitudinal axis with respect to the outer peripheral surface of the insertion portion A tapered portion having a cylindrical shape which is detachably disposed with respect to the tapered portion and has an inner diameter of the tapered portion increased so as to allow the insertion portion to be inserted through the tapered portion The tapered portion holding the state to restrict the inner diameter of the tapered portion from decreasing in diameter and being detached as the insertion portion is inserted into the tapered portion so that the distal portion of the insertion portion And a reduced diameter regulation body that exerts a diameter reduction force in a range slidable in the direction around the axis of the longitudinal axis with respect to the outer peripheral surface of the reduced diameter regulating body.スパイラルユニットは、その外周面に螺旋フィンを有するチューブ体と、長手軸に沿って設けられ、前記チューブ体に近接する近位及び離隔する遠位を有し、その外周が前記長手軸に沿って前記近位よりも前記遠位の方が前記長手軸に向かって縮径され、前記遠位で挿入部の外周面に対して前記長手軸の軸回り方向に摺動可能な範囲で縮径力を発揮させる筒状のテーパ部と、前記テーパ部に対して取り外し可能に配設され、前記テーパ部に前記挿入部が挿通されるのを許容するように前記テーパ部の内径を拡径させた状態を保持して前記テーパ部の内径が縮径するのを規制し、前記テーパ部に前記挿入部が挿通されるのに伴って取り外されることによって、前記テーパ部に前記遠位で前記挿入部の外周面に対して前記長手軸の軸回り方向に摺動可能な範囲で縮径力を発揮させる縮径規制体とを有する。
