PURPOSE: To surely pour a grinding liquid on the grindstone surface, to prevent the grindstone from its temperature rising and to prolong the service life, by providing more than three nozzles which inject the grinding liquid at high speed toward a diamond grindstone around the grindstone and approximately equaliz ing each center angles that adjoining two optional nozzles form for the grind stone center.

CONSTITUTION: More than three nozzles 5 which inject a grinding liquid at high speed toward a diamond grindstone 3 are provided around this grindstone 3. Moreover each center angles that adjacent two optional nozzles 5 form for the grindstone 3 center are approximately equalized. Consequently, instantaneous point cooling is continuously performed for the grinding point of the grindstone 3 with the grinding liquid injected from each nozzles 5, grinding chips are simultaneously washed out and the clogging of the grindstone is prevented.