Abstract: An R-T-B based permanent magnet powder, which has been made by an HDDR process and which has an average crystal grain size of 0.1 ?m to 1 ?m and a crystal grain aspect ratio (ratio of the major axis size to the minor axis size) of 2 or less, is provided (Step (A)). R is a rare-earth element, of which at least 95 at % is Nd and/or Pr, and T is either Fe alone or Fe partially replaced with Co and/or Ni and is a transition metal element, of which at least 50 at % is Fe. Meanwhile, an R?—Cu based alloy powder, which is made up of R? and Cu, which accounts for 2 at % to 50 at % of the alloy powder, is also provided (Step (B)). R? is a rare-earth element, of which at least 90 at % is Nd and/or Pr but which includes neither Dy nor Tb. The R-T-B based permanent magnet powder and the R?—Cu based alloy powder are mixed together to obtain a mixed powder (Step (C)). And then the mixed powder is subjected to a heat treatment process at a temperature of 500° C. to 900° C.