The super heat resisting alloy Inconel 718 used in gas turbines is known as difficult-to-machine materials. Under the same cutting conditions, the tool wear progresses at a noticeably quicker pace than that in cutting metals such as carbon steel. At the present time, the cutting speed is reduced during machining Inconel 718. There is an increasing demand for more efficient cutting in this field. Accordingly, a high speed cutting was attempted at increased cutting fluid flow rate by injecting fluid at a high pressure to the cutting edge. As a result, as the injection speed of the cutting fluid went up, the cutting temperature was reduced and the flank wear was reduced. And these experiments showed the prospective result that the cutting speed could be increased with high pressurized cutting fluid (high pressure injection). In the next step, cutting of Inconel 718 was attempted by using a rotary tool under the high pressure injection. Furthermore, the flank wear was reduced and the tool life could be improved.