To synthesize three-dimensional shape data as a favorable carving data, and also, efficiently perform a carving by the three-dimensional shape data.

This three-dimensional shape data processing device which processes three-dimensional shape data being formed on a flat plate, is equipped with synthesize-processing means 5, 6 which partially superpose the three- dimensional shape data, and synthesize-process by remaining either one of the three-dimensional shape data at the superposed region, and deleting the other three-dimensional shape data, and an interpolation processing means 7 which performs an interpolation process by providing a fixed interpolation region on a border of the synthesized three-dimensional shape data, and an interpolation is performed in such a manner that the height may be continuously changed in the synthesized three-dimensional shape data through the interpolation region. A carving device 9 prevents chips from being welded to a cutting blade and a plate to be carved even in the case of noble metals by performing a cutting while dipping the flat plate in a cutting oil, and the carving quality can be improved.