PURPOSE: To generate a line data for machining the relief part of a metal mould rapidly and easily by providing a three-dimensional offset processing means to offset three-dimensionally relief process area data in the specified direction, and at the same time, providing a three-dimensional offset process means to store the offset data.

CONSTITUTION: A relief process area data extracting means 7 to extract the relief process area data by the data from a digitizing data process means 4 and relief process area line data process means 6 is provided. Furthermore, a three-dimensional offset process means 8 to offset the relief process area data three-dimensionally and to store it by the data from a process condition data process means 5 and the relief process area data extracting means 7 is provided. Then, a relief process line data is generated and stored in a relief process line data process means 9 by the data from the process condition data process means 5 and the three-dimensional offset process means 8.