An excision instrument includes a blade 2 mounted on the back surface of an elastic member 5 provided between gripping extensions 3, and is used by bringing the gripping extensions 3 close to each other to curve the elastic member 5 together with the blade 2 and by putting the convex surface produced on the blade 2 in a portion-to-be-removed. In the top surface of the elastic member 5, a plurality of slits 8, 9 and 10 are provided, and a plurality of projections 11 are provided between the slits 8, 9 and 10 so that contact parts 11a of the projections 11 are brought close to and into contact with each other via the slits 8, 9 and 10 when the elastic member 5 is curved. The contact parts 11a function as a curvature restricting part for restricting the curvature of the elastic member 5 or a flexural rigidity changing part for changing the flexural rigidity of the elastic member 5.