PURPOSE: To provide an efficient cutting process by applying jet water or nonflammable oil onto a cutting plate, applying simultaneously jet air to cool the material to be cut together with preventing thermal resistance cutting chip from wetting.

CONSTITUTION: A hot material 4 is transferred along a roller 11 and a cutter 1 rotates around a shaft 3 cutting the material. Thermal resistance cutting chips 2 are fixed on the outer circumference of the cutter 1. Because the chips 2 are apt to break with thermal shock, cooling water 9 is applied through jet from a nozzle 5 onto a cutter plate 1. If the chips 2 is sprayed with water stream 7 life of them is shorten. In order to control the water stream 7, air 10 jets from a nozzle 6 along a direction 8. Consequently, the cutter 1 can be cooled without wetting of the chips 2. Also, when grooves 13 are formed in a cutter plate and a cover 12 covers a circumferential portion 17, cooling can be effected without wetting of the chips. By controlling water volume and air volume through regulator valves 15, 14, cutting face of the material can be kept at a suitable temperature.