A method includes: manufacturing a sintered compact represented by (Rl)x(Rh)yTzBsMt and has a grain boundary phase; manufacturing a rare earth magnet precursor from the sintered compact; and performing a heat treatment on the rare earth magnet precursor at 450° C. to 700° C. to diffuse and to infiltrate a melt of a modified alloy containing a light rare earth element and either a transition metal element, Al, In, Zn, or Ga into the grain boundary phase. Rl represents a light rare earth element. Rh represents Dy or Tb. T represents a transition metal containing at least one of Fe, Ni, and Co. B represents boron. M represents at Ga, Al, or Cu. x, y, z, s, and t represent mass % of Rl, Rh, T, B, and M. Following expressions are established: 27≤x≤44, 0≤y≤10, z=100−x−y−s−t, 0.75≤s≤3.4, 0≤t≤3. An infiltration amount of the modified alloy is 0 mass % to 5 mass %.