PURPOSE: To give a powerful bearing force and a stabilizing force as well as to improve an operational efficiency by a method wherein an open leg material is made open its legs to the vertical direction to a pile main body in conjunction with a driving of a pile main body, and a bulking material is poured into the inside of the pile main body.

CONSTITUTION: Proper number of open leg materials 1 which are freely rotate to almost a right angle with the pile are fitted through a pivot to a pin 3 which is fitted with a shaft in a side wall or coupled in a free sliding way with a side wall of a downward cylindrical pile main body 4, and then, along the open leg material 1, a force receiving board 2 is mounted from the inside of the pile and a hook 5 for prevention of leg opening is installed at the point or a middle part of the open leg material 1. A leg opening prevention pin to supress the opening legs having a point inserted with a coupling rod or a rope from the upper part of the pile is inserted into the hook 5. A rigidity reinforcement material 6 is formed at the upper part of the pin 3. In conjunction of a driving, the open leg material 1 is made to open its legs to the right angle with the pile and a filling material is poured into the inside of the pile main body to be solidified and fixed.