PURPOSE: To manufacture the steel tube with high strength by forcibly pressing and forming the steel plate in inside of steel tube by the same interval.

CONSTITUTION: A hole is made at the center of the steel plate, and notches are made on the edge. This is forcibly pressed in the steel tube. Notches of the outer circumference of steel plate is properly smashed and the work is executed smoothly. By plating the manufactured steel tube, the one body formings of seamless is made. Therefore, the strength of steel tube against the collapse can be improved largely. The interval of partition wall is made more narrow so the effect is higher, but an ideal interval is naturally decided on respective specifications on the relation of weight and cost. And there is the same effect for a round type, a square type and all kind of types of steel pipe. By using these, the capacity of every thing of a bicycle, an autobi, an aerospace relations, and a high-rise building material, etc., can be improved.