When decarburization blowing is carried out using a top-blow lance having at least one independent system of gas feed pipes; while the nozzle absolute secondary pressure Po of the lance of at least one system is kept in a range of 0.7 to 2.5 times the nozzle optimum expansion absolute secondary pressure P of the lance, the oxygen feed speed is changed by changing the nozzle absolute secondary pressure during the blowing by the system so that its maximum value is at least 1.1 times its minimum value. The top-blow refining method uses a top-blow lance having a slit-like nozzle which has two to ten shield portions disposed at a part of the opening at the end of the lance, has a concentric polygonal or circular cross section, has a ratio B/h of 10 to 225 where B (mm) is the long side of the openings separated by the shield portions and h (mm) is the short side, and has a value (B.h)R of 0.4 to 4 mm where R (mm) is the lance diameter R (mm), and one to six circular nozzles connected to a gas feed pipe independent of the slit-like nozzle and disposed inside the concentric polygon or circle.