To provide a medical instrument that enables a functional portion to be displaced adequately even in a small bending angle, by making a structure that enables a large dimension in the longitudinal direction of the shape-memoryportion to be secured without particularly increasing the length dimension of the entire instrument, a medical instrument is provided with a rod-shaped grasp portion 1 at a base end thereof, a functional portion 3 used in medical practice at a front end thereof, and a shape-memory portion 2 comprised of a rod-shaped shape-memory alloy provided between the grasp portion 1 and the functional portion 3, and the grasp portion 1 is provided with a holding portion 1A having a space in which one end of the shape-memory portion 2 is inserted from the longitudinal direction. The instrument has a gap between an outer surface of the shape-memory portion 2 and an inner surface of the holding portion 1A, and in bending the shape-memory portion 2, the shape-memory portion 2 is capable of deforming within the range of the gap. Then, by bending, the outer surface of the shape-memory portion 2 comes into contact with an inner edge portion of an opening of the holding portion 1A, and thereby restricts deformation of the shape-memory portion 2 beyond the predetermined range.
