The present invention relates to a data generating device, a data generating method and a data generating program for generating numerical data for controlling the operation of a cutting tool when machining an article. A data generating device 10 of the present invention comprises geometric data input means 26 to which a set of geometric data representing a shape of said article to be machined is input, partial geometric data generating means 28 for dividing the set of geometric data into a plurality of sets of partial geometric data each representing one of a plurality of article parts constituting said article to be machined, a plurality of partial numerical control data generating means 16,18,20,22,24 for generating from said sets of partial geometric data sets of partial numerical control data for machining article parts represented by the partial geometric data and numerical data unifying means 30 for generating a set of numerical control data for machining the whole of said article to be machined by unifying the plurality of sets of said partial numerical control data.