PURPOSE: To obtain a rolling mill capable of finishing a thin steel billet, having 20W50mm thickness and manufactured by a continuous casting method, into a hot rolled steel sheet at a low intial investment, by further reducing the thickness of a material, rolled by horizontal rolls with the aid of a die provided to the outlet side of a roll gap.

CONSTITUTION: A rolling material 11 of thin cast billet is pushed into a four high mill 13 by applying a compressive force to it from its rear side while rolling it by a push-in rolling mill 14, to roll it between the work rolls W1, W2 of the mill 13. The material 11 is further extruded by a fixed die 2 at the same time, to reduce the material thickness into a prescribed one. The application of the compressive force from rear side by the mill 14 is not required when only the push-in force of mill 13 is enough for the extrusion. Further, the material 11 can be rolled and extruded to the limit of producing a buckling between the rolls W1, W2 and the die 2, by setting the die 2 at the downstream of the outlet of roll gap. Accordingly, the material 11 is perfectly prevented from being forced out between the rolls W1, W2 and the die 2.