A medical instrument is disclosed, which includes an elongated member having a plurality of joint members arranged side by side in an axial direction, the elongated member taking a first form that is bendable in a direction intersecting with the axial direction when the joint members are arranged with gaps therebetween in the axial direction and taking a second form having rigidity when the distance between the joint members is reduced in the axial direction to be narrower than the distance in the first form, a gripper capable of gripping an object to be gripped, and a first push-pull member and a second push-pull member each movable along the axial direction of the elongated member. Operating the first push-pull member and the second push-pull member enables the elongated member to be switched between the bendable first form and the rigid second form and enables an opening-closing operation of the gripper.
