PURPOSE: To facilitate production of a steel billet and to simplify the equipment by connecting a mold block having cross section corresponding to sectional shape of the steel billet to circulating state and arranging weirs at lower position side of pouring basin part formed.

CONSTITUTION: Multiple mold blocks 20 are circulately connected and also driving pulleys 21, 22 running the mold blocks 20 are arranged. In the mold block 20, inner space 24 according to the shape of the desired rough-shaped steel billet is formed. Then, to the pouring basin part 4 constituting of the mold block 24 the weir 26 is arranged at the lower position side thereof to slip with inner wall of the block 20. At the time of pouring the molten metal 8 from a pouring apparatus 7, the pouring basin part 4 is formed in the inner space 24 of the block 20. Then, a cooling device 8 is uniformly cooled and the molten metal 8 develops solidified shell and the rough-shaped steel billet 25 is continuously obtd. By this method, the production of the steel billet 25 is facilitated and the equipment is simplified.