To provide an offset processing apparatus for avoiding a fatal defect of shape data by creating a plurality of partial offset curved surfaces having no inversion and no self interference.

The offset processing apparatus creates the offset curved surface to an original curved surface based on the three-dimensional curved surface data and an offset value. The offset processing apparatus comprises a curved surface region dividing section for dividing the original curved surface into a normal region and a torsion region, a normal region offset processing section for creating the offset curved surface to the normal region, and a torsion region offset processing section for creating the offset curved surface to the torsion region. The offset curved surface to the normal region and the offset curved surface to the torsion region are synthesized, and an offset shape as the plurality of curved surfaces having no inversion and no self interference is created for one curved surface.

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