A method for producing an RFeB system magnet with high coercivity by preventing a coating material from peeling off the surface of a base material during a grain boundary diffusion treatment is provided. A method for producing an RL2Fe14B system magnet which is a sintered magnet or a hot-deformed magnet containing, as the main rare-earth element, a light rare-earth element RL which is at least one of the two elements of Nd and Pr, the method including: applying, to a surface of a base material M of the RL2Fe14B system magnet, a coating material prepared by mixing a silicone grease and an RH-containing powder containing a heavy rare-earth element RH composed of at least one element selected from the group of Dy, Tb and Ho; and heating the base material together with the coating material. Improved coating and base materials adhesion facilitates transfer of RH into base material grain boundaries.