PURPOSE: To economically manufacture the molten iron at an excellent heat efficiency by passing raw materials such as iron ores, cokes and limes in a spiral pipe whose diameter is increased downward, and feeding reducing hot gas upwardly against the flow of the raw materials.

CONSTITUTION: The mixed raw materials such as iron ores, cokes both for fuel and for reduction, and limes as the slag-making agent are fed into an inclined guide plate assembly 24 from a hopper 16 through a small bell 18 and a large bell 20. The mixed raw materials 25 flow down in a spiral pipe 28 from an inlet 26 of the spiral pipe 28 which is formed conical. An outlet 30 of the spiral pipe 28 is opened in a hearth, and oxygen 38 is blown from a lance 48 and a plurality of burners 36, 38 provided in the middle of the spiral pipe 28 to burn cokes, and the molten iron and molten slag are manufactured through the reduction and melting of the iron ores by the heat and CO in the combustion gas, inexpensive steel scrap 50 is added to the hearth 14, the furnace gas is fed to a gas cleaner 44 by a gas uptake 22, and re-circulated in the spiral pipe 28 to manufacture the molten iron at a low cost by making use of the effectively combustible composition.