A kinematic model arithmetic portion calculates a coordinate value (ze1 (θe)) as distance information indicating the distance between a member that serves as a reference surface for the curve shape of a curvable portion and a member in the curvable portion that is closest to the reference surface. A switch determination unit determines based on the coordinate value whether to drive a wire for driving the curvable portion by a drive displacement calculated for the wire along with the coordinate value by the kinematic model arithmetic portion.