R-T-B-based sintered magnet

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An R-T-B system sintered magnet is provided which achieves both a high residual magnetic flux density and a high coercive force. The R-T-B system sintered magnet comprises main-phase grains 1 each having a core-shell structure comprising an inner shell part 2 and an outer shell part 3 surrounding the inner shell part 2, wherein the concentration of the heavy rare earth element in the inner shell part 2 is lower by 10% or more than the concentration of the heavy rare earth element in the periphery of the outer shell part 3, and (L/r) ave falls within a range from 0.03 to 0.40 in the main-phase grains 1 each comprising the inner shell part 2 and the outer shell part 3, wherein L represents the shortest distance from the periphery of the main phase grain 1 to the inner shell part 2, r represents the equivalent diameter of the main phase grain 1, and (L/r) ave represents the average value of L/r for the main-phase grains 1 present in the sintered body and having the core-shell structure.