PROBLEM TO BE SOLVED: To provide a medical device which reduces an event of the separation of a cutting member in expanding and contracting an expanding and contracting member in a radial direction and hardly obstructs expanding and contracting movements of the expanding and contracting member by the cutting member.SOLUTION: In a medical device 1, a distal end 11 of an expanding and contracting member 10 and a distal end 21 of a cutting member 20 are firmly fixed on a distal end tip 40, and a proximal end 12 of the expanding and contacting member 10 and a proximal end 33 of a core wire 30 are firmly fixed on a ring 50. The core wire 30 inserted in a hollow part 22 of the cutting member 20 from a proximal end direction is movable in the hollow part 22 in a longitudinal direction in association with the expansion and contraction of the expanding and contracting member 10. The cutting member 20 can move to an optimal position by the core wire 30 inserted in the hollow part 22 without separating from the expanding and contracting member 10 in association with the expansion and contraction of the expanding and contracting member 10. Further, the core wire 30 can be separated from the hollow part 22 of the cutting member 20. (The core wire 30 and the cutting member 20 are separated from each other.)SELECTED DRAWING: Figure 1【課題】拡縮部材を径方向に拡縮させた際に切込み部材が外れてしまうことを低減し、かつ、拡縮部材の拡縮の動きが切込み部材により阻害されにくい医療用デバイスを提供する。【解決手段】医療用デバイス１では、拡縮部材１０の先端１１と切込み部材２０の先端２１とが、先端チップ４０に固着されており、拡縮部材１０の後端１２とコアワイヤ３０の後端３３とが、リング５０に固着されている。切込み部材２０の中空部２２に後端方向から挿入されたコアワイヤ３０が、拡縮部材１０の拡縮に伴って、中空部２２内を長手方向に移動可能になっている。切込み部材２０は、中空部２２内に挿入されたコアワイヤ３０により、拡縮部材１０の拡縮に伴って、拡縮部材１０から外れることなく、最適な位置に移動することができる。また、コアワイヤ３０が切込み部材２０の中空部２２から離脱する（すなわち、コアワイヤ３０と切込み部材２０とが互いに分離する）ことができる。【選択図】図１
