PURPOSE: To easily obtain a complete round flange by welding a cut part, after pressing an annular plate obtained by cutting a long size coil in the axial direction, and thereby dispensing with a correction after deposition.

CONSTITUTION: A material f1 is coiled. One side of the coiled material f2 is cut off in the shaft direction, and separated into annular plates f3 by each coil. While the cut part 8 of the separated annular plate f3 is horizontally supported by a pressing roller from the above, the outside of the cut part 8 is pressed to a specifically spaced position by a pushing side base towards a fixed side base and formed into an elliptic annular plate f4. The cut part 8 of the elliptically formed annular plate f4 is horizontally fixed and welded by flash butt welding. The burrs 33 produced around the welded part are removed, and a complete round flange f6 is formed.