To prevent the shrinkage in the width direction, and to improve the yield by providing notches of the depth of specified ratio to the dimension of opposite sides of an octagon over the whole periphery in a border between a riser part and a steel ingot body before a tong part holding margin of square section is manufactured by the riser part, and adding the intermediate octagonal form rolling in the process to form a tong part at the riser part.

A cold shut 13 between a riser part 2 and a steel ingot body 1 is lightly rolled in an octagonal shape by a pair of upper and lower flat dies and a stepped part is removed thereby. A draw is formed on the whole periphery of a steel ingot at the octagonal cold shut 13 using a chisel. The depth of the draw is preferably 10-20% of the dimension of opposite sides of the octagon. Only the riser part 2 is rolled using a pair of upper and lower flat dies to form a tong part 3. If the depth of the draw is too small, the steel ingot body 1 flows into the tong part 3, and the body 4 flowing into the tong part is increased in quantity. If the depth of the draw is too large, the part of the draw is bent or cut when the steel ingot body 1 is forged to the specified dimension.