To instantly replace a tool by an operator when the service lift of the tool is completed by providing a display control means to control so as to display that the tool service life is almost completed to a display means when a preset tool service life previously announcing value and a value by an operation coincide with each other.

When judged that it is cutting moving time, the service life of a tool using at present is subtracted by using an internal timer. When judged that a work program finishes, the service life stored in a RAM 32 and the previously announcing service life are compared with each other with every tool, and tools whose service life reaches the previously announcing service life are all extracted. Afterwards, whether or not there is an extracted tool is judged, and when judged that there is the extracted tool, a warning message that the tool service life is almost completed is displayed on a CRT 6 together with its tool number.