To faithfully reproduce an intaglio image with a high quality against a line drawing original image by preparing an NC machining tool cutter path by carrying out a shrinkage processing due to a specific distance space in consideration to a depth value plural times against a line drawing data on which a line drawing pattern is inputted on a paper substance and engraving on a metal substrate.

An outline trace is carried out against a bit map image to which a line drawing manuscript is inputted by a high resolution flat bed scanner and finally, an outline V0 of a line drawing image is obtained as a vector data. Until an outline inside of a line drawing image produces an engravable cutter path just enough, a subsequent shrinkage processing is repeated to obtain cutter pathes V1, V2, V3. A text processing for imparting a machine control code to each cutter path prepared is carried out to make a NC machining tool data of four axle control. An intaglio image with a high quality having an accurate depth value, a cross section shape of a desired picture line and a padding shape is engraved on a substrate such as metal based on the data.