To decorate the surface of a material to be worked through the creation of decorative characteristic by generating a knife mark with a specific width when the surface of the material is worked by rotary cutting.

Parameters are set which are the state, number and array of cutting blades, the shape and diameter of a cutting edge, blade length and also, cutting conditions such as the number of rotation and depth of cut of a rotary cutting tool, the feed speed of a material and its form, e.g. combination of decorative laminated monolayer or multilayer material. If the width Wa of a knife mark formed by cutting is 5mm or less, it is too fine to be recognized as a mark for decoration, and it is recognized as a mere knife mark. On the contrary, if the width is 150mm or more, the feed speed of the material is too high for the number of rotation of the cutting tool, so that there are difficulties in the working. Thus it is possible to numerously create a decorative pattern on the surface of the material.