PURPOSE: To make it possible to carry out efficiently lubrication and cooling of a blade part and discharge of chips when cutting is carried out, by flowing out a cooling medium from the outer circumferential part of a rotating blade by using the rotating blade having a path formed, wherein a fluid is passed through.

CONSTITUTION: A cooling medium is flowed into a perforated hole 15 side from an open end 27 of a rotating blade 10 of a fluid path 26 through a groove 16 set in a fixing hole of the rotating blade 10, flowed out to the outer circumference of the blade part 14 from the perforated hole 15 through the hole and spouted to the cut part 34 of an object 33. When the cut part 34 is cut deeply and becomes to a groove shape, chips tend to be accumulated in the cut path 34, but the chips are flowed out to the outside of the cut part 34 by the spouted cooling medium 32 and the blade part 14 is cooled by taking the heat away by the cooling medium 32 to prevent deterioration of the rotating blade 10. Sounds of collisions between the blade part 14 and the cut object 33 and between the blade part 14 and chips are both reduced and as the result, noise in cutting is reduced.