Method for regulating a path of an instrument

A method for regulating a path of a tool is provided to prevent damage to the tool by editing a process path by considering a shape of the tool and the material used in a numerical control process through a numerical control process simulation using original numerical control data. A tool path modifying apparatus receives at least one material shape information and tool information and original numerical control data(304). The tool path modifying apparatus perform a numerical control process simulation by using the original numerical control data, selected material shape information, and the tool information(310). If the damage is determined through the numerical control process simulation by colliding the tool of the selected tool information with the material of the selected material shape information, the tool path modifying apparatus edits the tool path newly and generates the final numerical control data(318).