The cross-sectional shape data of a three-dimensional model is divided according to work small areas obtained by dividing a work entire area where optical shaping work is performed into a plurality of areas, and work small area data which is cross-sectional shape data corresponding to said work small areas is generated. Also, the work small area data is enlarged with offset width based on the contracting ratio of a light hardening resin, and areas, which are wider than the work small areas on the surface of the light hardening resin by the offset width, are subjected to one-shot exposure based on the enlarged work small area data to form a hardening layer for each of the work small areas. The present invention can be applied to, for example, an optical shaping apparatus.