To make the block mill compact, to facilitate its maintenance and repair, and to roll the wire rod and the bar steel with desired dimensional precision and in a desired shape by providing a fluid shaft coupling type or viscous multiple disc clutch type tension controller on the drive shaft of a rolling stand.

Between the drive part M of the block mill and the drive transmission shafts 5 of rolling stands 3, torque converters 61 or viscous couplings 62 allowing to slide, are mounted. The drive transmission shafts 5 of the rolling stands 3 and the drive part M can be separated, and tension generated among the rolling stands 3 by the dispersion of the shape and the dimensions of a material R to be rolled and the dispersion of temperatures, can be absorbed. When the rotational speed of the drive transmission shafts 5 of the rolling stands 3 becomes slower than that of the drive shafts 4, even when the rotational speed of the rotating shafts 4 is in an optimum pass schedule, it can cope with the fluctuation of the tension by the torque converters 61 and viscous coupling 62. It is important that the rotational speed of the drive shafts 4 is higher tan the rotational speed of the optimum pass schedule.