A medical device configured to permit free-adjustment of the curvature-factor by which the region connected to the distal member provided with the medical-treatment member is to be curved. The medical device includes an elongated body having an opening portion at the distal end, a distal member provided with a medical-treatment member held by the elongated body freely movably in an approaching and separating manner with respect to the opening portion, and an operation member. The operation member includes a first member which is connected to the distal member and which transmits a force, that separately-moves the distal member relatively with respect to the elongated body, to the distal member and a second member connected to the distal member, in which caused by the cooperation between the first member and second member, it is possible to freely-adjust the curvature-factor by which the first member is curved.
