An alloy for R-T-B-based rare earth sintered magnets which contains R which is a rare earth element; T which is a transition metal essentially containing Fe; a metallic element M containing one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied,
0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36 Formula 1
wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.