R-T-B based permanent magnet

An R-T-B based permanent magnet (1) which comprises a magnet body (2) comprising a sintered product comprising a main phase comprising R2T14B crystal grains (wherein R represents one or more of rare earth elements, and T represents one or more transition metals comprising Fe or Fe and Co) and a grain boundary phase containing R in an amount more than that in the main phase and, formed in the surface layer portion thereof, a hydrogen-rich layer (21) having a hydrogen concentration of 300 ppm or more and having a thickness of 300 mum or less (exclusive of zero), and a protective coating film (3) covering the surface of the magnet body (2). The R-T-B based permanent magnet (1) exhibits the corrosion resistance being improved by the protective coating film (3) without the deterioration of magnetic characteristics, and the protective coating film (3) may be formed by electrolytic plating. The R-T-B based permanent magnet (1) can secure the satisfactory corrosion resistance, which is the object of the formation of the protective coating film (3), with little reduction of the efficiency in the production, and also is reduced in the partial disintegration (falling of grains) in the surface thereof and thus exhibits high dimensional precision.