To provide an automatic grinding blade which is molded to be always automatically ground when the blade of a stone mill is worn.

The conventional blade of the stone mill has a part for crushing grains which is almost obtuse in a cross section. By making the part for crushing grains to be acute and adding a part for shearing the grain to the stone mill, a speed with which the grains are powdered is made faster and the performance of the mill is improved. The blade can be machined to be acute since tools for machining a stone material have been developed, and there is a deep-rooted demand for the stone mill but are almost few craftsmen for stone mill management including production as repeatedly described in application documents. For above reasons, a method for enabling the blade of the stone mill to be automatically ground has been successfuly developed. Nowadays, small inexpensive stone mills for crushing a variety of dry foods as well as grains, including those using a method for electrically rotating the upper mill, are expected to become popular again as a way to add colors to life.