PURPOSE: To stably execute the searfing of bead on the case of the manufacturing line speed of the shapes, and to easily treat the slag and the plasma gas generated at the scarfing time from sticking on the high speed scarfing method and device.

CONSTITUTION: On the shapes manufacturing line of the high line speed, the bead 3 is molten with the plasma arc from the plasma torch 4, also the molten metal of this molten bead is blowed away by using the blow from the assitant blow nozzle 5 set on rear step of the plasma torch in the flow direction of the manufacture line, the scarfing surface is made flat, the slag is reduced from sticking by wetting on the front surface of the above shaped steel at a preceding stage of the above plasma torch on the line flow direction for manufacturing.