PURPOSE: To speed up rolling and separation and to prevent the buckling of small-diameter rolling materials by driving the upper and lower rollers of a separator and a pair of upper and lower rollers of a pinch roller part while interlocking the driving thereof by timing belts.

CONSTITUTION: A splitter 6 which consists of a pair of upper and lower driving rollers 1, 2 and forms a fine groove 4 for sepn. in the thin-walled part is attached to a driving side frame 20. The separator which separates up and below steel bars 10 from the adjacent preforming parts for steel bars emitted from the splitter 6 by means of a guide part 8 for pushing down the preforming part and a guide part 9 for pushing up the preforming part is attached to the frame. The pinch roller part 14 which guides the steel bars 10 from above and blow and delivers forcibly the steel bars is disposed. The frames on the driving side and work side are coupled by a hinge and is made freely openable and closable. The high-speed separating operation of the billets is thus made possible and the easy exchange of rollers, etc. is made possible.