The method for manufacturing molten irons, comprising steps of: reducing mixtures containing iron ores in a reduction reactor and converting the mixtures containing iron ores into reduced materials; preparing lumped carbonaceous materials containing volatile matters, the volatile matters contain carbon and hydrogen, as a heating source for melting the reduced materials; charging the lumped carbonaceous materials into a dome-shaped upper portion of a melter-gasifier and forming a coal packed bed; preparing fine carbonaceous materials containing volatile matters as a heating source for melting the reduced materials by crushing raw coals; injecting oxygen and the fine carbonaceous materials into the coal packed bed through a tuyere installed in the melter-gasifier; charging the reduced materials into the melter-gasifier connected to the reduction reactor and manufacturing molten irons; and supplying reducing gas in the melter-gasifier made from volatile matters contained both in the lumped carbonaceous materials and the fine carbonaceous materials to the reduction reactor wherein the lumped carbonaceous materials contain volatile matters in the range from 20.0wt% to 35.0wt% in the step of preparing lumped carbonaceous materials containing volatile matters as a heating source for melting the reduced materials; and wherein the grain size of the lumped carbonaceous materials is in the range from 8mm to 35mm; and wherein a grain size of the crushed fine carbonaceous materials is not more than 3mm in the step of injecting fine carbonaceous materials into the coal packed bed; and wherein the fine carbonaceous materials contain volatile matters of the range from 8.0wt% to 35.0wt%, and the volatile matters contain carbon and hydrogen in the step of preparing fine carbonaceous materials containing volatile matters as a heating source for melting the reduced materials. reducing mixtures containing iron ores in a reduction reactor and converting the mixtures containing iron ores into reduced materials; preparing lumped carbonaceous materials containing volatile matters, the volatile matters contain carbon and hydrogen, as a heating source for melting the reduced materials; charging the lumped carbonaceous materials into a dome-shaped upper portion of a melter-gasifier and forming a coal packed bed; preparing fine carbonaceous materials containing volatile matters as a heating source for melting the reduced materials by crushing raw coals; injecting oxygen and the fine carbonaceous materials into the coal packed bed through a tuyere installed in the melter-gasifier; charging the reduced materials into the melter-gasifier connected to the reduction reactor and manufacturing molten irons; and supplying reducing gas in the melter-gasifier made from volatile matters contained both in the lumped carbonaceous materials and the fine carbonaceous materials to the reduction reactor wherein the lumped carbonaceous materials contain volatile matters in the range from 20.0wt% to 35.0wt% in the step of preparing lumped carbonaceous materials containing volatile matters as a heating source for melting the reduced materials; and wherein the grain size of the lumped carbonaceous materials is in the range from 8mm to 35mm; and wherein a grain size of the crushed fine carbonaceous materials is not more than 3mm in the step of injecting fine carbonaceous materials into the coal packed bed; and wherein the fine carbonaceous materials contain volatile matters of the range from 8.0wt% to 35.0wt%, and the volatile matters contain carbon and hydrogen in the step of preparing fine carbonaceous materials containing volatile matters as a heating source for melting the reduced materials.