A treatment tool that includes an elongated shaft, a hollow socket connected to the shaft and having a first spherical surface with a constant radius, a ball inside the socket, and a wire extending through the shaft and causing a bending mechanism to bend. The rotation of the ball about a center point of the socket causes advancing and retreating of the wire. The ball includes a second spherical surface that is formed in a partial region of an outer surface of the ball, and that is configured to slide along the first spherical surface of the socket. The ball also includes a fixing portion attaching the wire to the ball, and a wire sliding surface on which the wire slides due to rotation of the ball.