A method for producing a sintered R-T-B based magnet, comprising: a step of providing a sintered R1-T-B based magnet work that contains R1: not less than 27.5 mass% and not more than 35.0 mass%, where R1 is at least one rare-earth element which always includes at least one of Nd and Pr, B: not less than 0.80 mass% and not more than 0.99 mass%, Ga: not more than 0.8 mass%, M: not more than 2.0 mass%, where M is at least one of Cu, Al, Nb and Zr, and T: 60 mass% or more, where T is Fe, or Fe and Co, the Fe content accounting for 85 mass% or more in the entire T; a step of providing an R2-Ga alloy, where R2 is at least two rare-earth elements which always include at least one of Tb and Dy and at least one of Pr and Nd; and 50 mass% or less of Ga can be replaced by at least one of Cu and Sn; a diffusion step of, while keeping at least a portion of at least a portion of the R2-Ga alloy in contact with at least a portion of a surface of the sintered R1-T-B based magnet work, performing a first heat treatment at a temperature which is not lower than 700°C and not higher than 950°C in a vacuum or an inert gas ambient, to increase a content of at least one of Tb and Dy in the sintered R1-T-B based magnet work by not less than 0.05 mass% and not more than 0.40 mass%; and a step of subjecting the sintered R1-T-B based magnet work having undergone the first heat treatment to a second heat treatment at a temperature which is not lower than 450°C and not higher than 750°C but which is lower than the temperature of the first heat treatment, in a vacuum or an inert gas ambient, wherein the sintered R1-T-B based magnet work satisfies eq. below: T / 55.85 > 14 × B / 10.8 where is the T content by mass%; and is the B content by mass%, except for Samples 16-19 in Example 3 in EP3503130A1. a step of providing a sintered R1-T-B based magnet work that contains R1: not less than 27.5 mass% and not more than 35.0 mass%, where R1 is at least one rare-earth element which always includes at least one of Nd and Pr, B: not less than 0.80 mass% and not more than 0.99 mass%, Ga: not more than 0.8 mass%, M: not more than 2.0 mass%, where M is at least one of Cu, Al, Nb and Zr, and T: 60 mass% or more, where T is Fe, or Fe and Co, the Fe content accounting for 85 mass% or more in the entire T; R1: not less than 27.5 mass% and not more than 35.0 mass%, where R1 is at least one rare-earth element which always includes at least one of Nd and Pr, B: not less than 0.80 mass% and not more than 0.99 mass%, Ga: not more than 0.8 mass%, M: not more than 2.0 mass%, where M is at least one of Cu, Al, Nb and Zr, and T: 60 mass% or more, where T is Fe, or Fe and Co, the Fe content accounting for 85 mass% or more in the entire T; a step of providing an R2-Ga alloy, where R2 is at least two rare-earth elements which always include at least one of Tb and Dy and at least one of Pr and Nd; and 50 mass% or less of Ga can be replaced by at least one of Cu and Sn; a diffusion step of, while keeping at least a portion of at least a portion of the R2-Ga alloy in contact with at least a portion of a surface of the sintered R1-T-B based magnet work, performing a first heat treatment at a temperature which is not lower than 700°C and not higher than 950°C in a vacuum or an inert gas ambient, to increase a content of at least one of Tb and Dy in the sintered R1-T-B based magnet work by not less than 0.05 mass% and not more than 0.40 mass%; and a step of subjecting the sintered R1-T-B based magnet work having undergone the first heat treatment to a second heat treatment at a temperature which is not lower than 450°C and not higher than 750°C but which is lower than the temperature of the first heat treatment, in a vacuum or an inert gas ambient, wherein the sintered R1-T-B based magnet work satisfies eq. below: T / 55.85 > 14 × B / 10.8 where is the T content by mass%; and is the B content by mass%, except for Samples 16-19 in Example 3 in EP3503130A1.