An R-T-B system rare earth sintered magnet having a high mechanical strength and excellent corrosion resistance is provided. The R-T-B system rare earth sintered magnet of the present invention comprises a sintered body comprising a main phase consisting of an R.sub.2T.sub.14B phase where R represents one or more rare earth elements and T represents one or more transition metal elements essentially containing Fe, or Fe and Co, and a grain boundary phase containing a higher amount of R than the above described main phase, wherein the surface of the above described sintered body is partially covered with a carbon compound layer. In the R-T-B system rare earth sintered magnet of the present invention, the area ratio of the partial surface of the above described sintered body covered with the above described carbon compound layer to the entire surface thereof is preferably between 10% and 90%.