A method of producing carbon steel and low-alloy steel in a basic oxygen furnace is disclosed, in which a blow of the bottom-blowing gas predominantly comprised of carbon dioxide is introduced into a molten metal through at least one nozzle provided in the bottom or side wall of said basic oxygen furnace at least partly during the period of time from the beginning of blowing to the tapping of the melt, and the flow rate of the bottom-blowing gas is 1/200 - 9/100 the rate of oxygen impinged upon the melt through a lance.