Abstract: Grinding machine comprising a rotary shaft vertically supportd by a housing, a whetstone mounted on the upper end of the shaft and having a top surface serving as a grinding surface, means for rotating the shaft by the pressure of tap water to rotate the whetstone at a high speed, water supply means for supplying water to the grinding surface at a suitable rate to form a layer of water thereon during the rotation of the whetstone and urging means for raising the shaft by the tap water pressure to urge the whetstone upward. The whetstone is upwardly urged to automatically control the grinding pressure on the article to be sharpened which is pressed against the grinding surface, while water is applied to the grinding surface at a suitable rate.