Control points needed to generate a curve becoming the route of a deformable linear structure from respective pieces of passing point information defined at two passing points are arranged and the initial arrangement of control points needed to generate a curve is determined by performing re-arrangement of the control points, on the basis of a positional relation between the control points thus arranged. The curve between two points is re-generated from the initial arrangement thus determined while modifying the arrangement of one or more control points, the re-generated curves are then evaluated and a curve meeting a predetermined condition is extracted from among the curves.