The present invention relates to an RFeB-based magnet in which a treatment (grain boundary diffusion treatment) for diffusing atoms of the heavy rare earth element RH is performed in a base material including an RLFeB-based sintered magnet obtained by subjecting crystal grains in a raw-material powder including a powder of an RLFeB-based alloy containing the light rare earth element RL, Fe and B to orientation in a magnetic field and then sintering the oriented raw-material powder, or an RLFeB-based hot-deformed magnet obtained by subjecting the same raw-material powder to hot pressing and then to hot deforming to thereby orient the crystal grains in the raw-material powder, and a method for producing the RFeB-based magnet.