In a method for producing an R—Fe—B based rare-earth sintered magnet according to the present invention, first, provided is an R—Fe—B based rare-earth sintered magnet body including, as a main phase, crystal grains of an R2Fe14B type compound that includes a light rare-earth element RL, which is at least one of Nd and Pr, as a major rare-earth element R. Thereafter, the sintered magnet body is heated while a heavy rare-earth element RH, which is at least one element selected from the group consisting of Dy, Ho and Tb, is supplied to the surface of the sintered magnet body, thereby diffusing the heavy rare-earth element RH into the rare-earth sintered magnet body.