A method for refining molten steel in vacuum degassing equipment, comprising the steps of: throwing a powder together with a carrier gas toward a bath surface of molten steel in a vacuum vessel of the vacuum degassing equipment through a central hole disposed at a central portion of a top blowing lance vertically movable in the vacuum vessel, wherein the powder is one, or two or more of manganese ores, manganese ferroalloys and CaO-based desulfurization agents, and wherein the degree of vacuum in the vacuum vessel during the throwing of the powder is 2.7 to 13.3 kPa; and supplying a hydrocarbon gas from a fuel ejection hole disposed on a periphery of the central hole and supplying an oxygen-containing gas from an oxygen-containing gas ejection hole disposed on the periphery, such that the powder falls on the molten steel while being heated with a flame formed by combustion of the hydrocarbon gas at a leading end of the top blowing lance; wherein a lance height of the top blowing lance is 1.0 to 7.0 m, the lance height being a distance between a static surface of the bath surface and the leading end during the throwing of the powder, a dynamic pressure P of a jet flow ejected from the top blowing lance is calculated from equations to below being 20.0 kPa or more and 100.0 kPa or less, P = ρ g × U 2 / 2 ρ g = ρ A × F A / F T + ρ B × F B / F T + ρ C × F C / F T + V P / F T / 60 U = F T / S T × 1 / 3600 S T = S A + S B + S C F T = F A + F B + F C where, in the equations to, P is the dynamic pressure (kPa) of the jet flow at an exit of the top blowing lance, ρ g is the density (kg/Nm 3) of the jet flow, ρ A is the density (kg/Nm 3) of the carrier gas, ρ B is the density (kg/Nm 3) of the oxygen-containing gas, ρ C is the density (kg/Nm 3) of the hydrocarbon gas, V P is the supply rate (kg/min) of the powder, U is the velocity (m/sec) of the jet flow at the exit of the top blowing lance, S T is the total of the sectional areas (m 2) of the central hole, the fuel ejection hole and the oxygen-containing gas ejection hole at the exit of the top blowing lance, S A is the sectional area (m 2) of the central hole at the exit of the top blowing lance, S B is the sectional area (m 2) of the oxygen-containing gas ejection hole at the exit of the top blowing lance, S C is the sectional area (m 2) of the fuel ejection hole at the exit of the top blowing lance, F T is the total of the flow rates (Nm 3 /h) of the carrier gas, the oxygen-containing gas and the hydrocarbon gas, F A is the flow rate (Nm 3 /h) of the carrier gas, F B is the flow rate (Nm 3 /h) of the oxygen-containing gas, and F C is the flow rate (Nm 3 /h) of the hydrocarbon gas. throwing a powder together with a carrier gas toward a bath surface of molten steel in a vacuum vessel of the vacuum degassing equipment through a central hole disposed at a central portion of a top blowing lance vertically movable in the vacuum vessel, wherein the powder is one, or two or more of manganese ores, manganese ferroalloys and CaO-based desulfurization agents, and wherein the degree of vacuum in the vacuum vessel during the throwing of the powder is 2.7 to 13.3 kPa; and supplying a hydrocarbon gas from a fuel ejection hole disposed on a periphery of the central hole and supplying an oxygen-containing gas from an oxygen-containing gas ejection hole disposed on the periphery, such that the powder falls on the molten steel while being heated with a flame formed by combustion of the hydrocarbon gas at a leading end of the top blowing lance; wherein a lance height of the top blowing lance is 1.0 to 7.0 m, the lance height being a distance between a static surface of the bath surface and the leading end during the throwing of the powder, a dynamic pressure P of a jet flow ejected from the top blowing lance is calculated from equations to below being 20.0 kPa or more and 100.0 kPa or less, where, in the equations to, P is the dynamic pressure (kPa) of the jet flow at an exit of the top blowing lance, ρ g is the density (kg/Nm 3) of the jet flow, ρ A is the density (kg/Nm 3) of the carrier gas, ρ B is the density (kg/Nm 3) of the oxygen-containing gas, ρ C is the density (kg/Nm 3) of the hydrocarbon gas, V P is the supply rate (kg/min) of the powder, U is the velocity (m/sec) of the jet flow at the exit of the top blowing lance, S T is the total of the sectional areas (m 2) of the central hole, the fuel ejection hole and the oxygen-containing gas ejection hole at the exit of the top blowing lance, S A is the sectional area (m 2) of the central hole at the exit of the top blowing lance, S B is the sectional area (m 2) of the oxygen-containing gas ejection hole at the exit of the top blowing lance, S C is the sectional area (m 2) of the fuel ejection hole at the exit of the top blowing lance, F T is the total of the flow rates (Nm 3 /h) of the carrier gas, the oxygen-containing gas and the hydrocarbon gas, F A is the flow rate (Nm 3 /h) of the carrier gas, F B is the flow rate (Nm 3 /h) of the oxygen-containing gas, and F C is the flow rate (Nm 3 /h) of the hydrocarbon gas.