To provide a pulverizing method by which a substance to be pulverized can be efficiently pulverized, a pulverizer capable of efficiently pulverizing a substance to be pulverized, and powders with small particle sizes.

The method for pulverizing a substance by impacting it comprises supplying gases including oxygen to a space containing a substance to be pulverized, as the substance is pulverized. Upon the pulverization of the substance to be pulverized, the amount of oxygen to be supplied per gram of the substance and per unit hour ranges from 0.0123 to 0.492 [mL×min-1×g-1]. Upon the pulverization of the substance, gases are supplied to satisfy the relationship represented by 0.10×10-2≤Y/X≤5.00×10-2, when the specific surface area of the substance or powders that are the pulverized products of the substance is X[m2/g] and the oxygen content of the powders is Y[wt.%].