A method for producing a sintered R-T-B based magnet, R being a rare-earth element and containing at least one selected from the group consisting of Nd, Pr and Ce with no exception, and T being at least one transition metal and containing Fe with no exception, the method comprising the steps of: preparing a coarse-pulverized powder of an alloy for the sintered R-T-B based magnet, the coarse-pulverized powder having an average particle size, d50, not shorter than 10 μm and not longer than 500 μm as measured by an airflow-dispersion laser diffraction method conformed to JIS Z 8825:2013 revised edition, under the conditions of a dispersion pressure of 4 bar, the measurement range of R2, and the calculation mode of HRLD; supplying the coarse-pulverized powder to a jet mill machine including a pulverization chamber filled with inert gas and pulverizing the coarse-pulverized powder to obtain a fine-pulverized powder having an average particle size not shorter than 2.0 μm and not longer than 4.5 μm; and forming a sintered body of the fine-pulverized powder, wherein the inert gas is supplied with moisture at a rate of not lower than 0.5 g and not higher than 6.0 g per 1 kg of the coarse-pulverized powder, and the sintered R-T-B based magnet contains oxygen at a content not lower than 1000 ppm by mass and not higher than 3500 ppm by mass, wherein the average particle size, d50, is measured by an airflow-dispersion laser diffraction method conformed to JIS Z 8825:2013 revised edition under the conditions of a dispersion pressure of 4 bar, a measurement range of R2, and a calculation mode of HRLD, and the amounts of oxygen, nitrogen and carbon are measured by use of a gas analyzer, respectively by a gas fusion-infrared absorption method, a gas fusion - infrared absorption method, and a combustion - infrared absorption method. preparing a coarse-pulverized powder of an alloy for the sintered R-T-B based magnet, the coarse-pulverized powder having an average particle size, d50, not shorter than 10 μm and not longer than 500 μm as measured by an airflow-dispersion laser diffraction method conformed to JIS Z 8825:2013 revised edition, under the conditions of a dispersion pressure of 4 bar, the measurement range of R2, and the calculation mode of HRLD; supplying the coarse-pulverized powder to a jet mill machine including a pulverization chamber filled with inert gas and pulverizing the coarse-pulverized powder to obtain a fine-pulverized powder having an average particle size not shorter than 2.0 μm and not longer than 4.5 μm; and forming a sintered body of the fine-pulverized powder, wherein the inert gas is supplied with moisture at a rate of not lower than 0.5 g and not higher than 6.0 g per 1 kg of the coarse-pulverized powder, and the sintered R-T-B based magnet contains oxygen at a content not lower than 1000 ppm by mass and not higher than 3500 ppm by mass, wherein the average particle size, d50, is measured by an airflow-dispersion laser diffraction method conformed to JIS Z 8825:2013 revised edition under the conditions of a dispersion pressure of 4 bar, a measurement range of R2, and a calculation mode of HRLD, and the amounts of oxygen, nitrogen and carbon are measured by use of a gas analyzer, respectively by a gas fusion-infrared absorption method, a gas fusion - infrared absorption method, and a combustion - infrared absorption method.