The change in grain-size composition and magnetic properties of powder prepared by grinding cast alloy Nd2Fe14B in a ball mill for different times is studied. It is shown that during grinding the coercive force of the powder increases uniformly at first reaching a maximum, and then it decreases. It is established that this phenomenon is not due to powder oxidation during grinding but a reduction in the level of particle uniaxial anisotropy caused by deformation of their surface layer during grinding. The change in coercive force of Nd 2Fe14B alloy powder on grinding obeys the same features that are observed with mechanical grinding of other uniaxial magnetic materials.