Abstract: The characteristics of the wire are calculated, the wire having a cross-sectional shape which is substantially uniform along its length and having a length long enough in comparison with a diameter being deformed. The wire is divided into a plurality of elements with predetermined spacing along the length. When the wire is deformed, the shape of the wire after the deformation is determined. In the determined shape, a tangential stiffness equation using the element as a basis is calculated, and the calculated tangential stiffness equation is translated into a tangential stiffness equation using the whole of the wire as a basis. A global stiffness equation representing the whole wire is calculated from the tangential stiffness equation obtained by the translation. A load or a displacement produced in each portion of the wire is calculated from the global stiffness equation and the determined shape of the wire.