PURPOSE: To obtain uniform excellent concrete by housing a bottomed cylindrical bag molded in size larger than the inside diameter of a pile pit by an impermeable sheet material and a reinforcing bar in the pile pit, placing concrete and expanding the bottomed cylindrical bag.

CONSTITUTION: A bottomed cylindrical bag 12 molded in a bottomed cylindrical shape by an impermeable sheet material using corrosion-resistant reinforced synthetic resin fibers is employed. The diameter of the bottomed cylindrical bag 12 is molded in size larger than the inside diameter of the pile pit 10. The bottomed cylindrical bag 12 is inserted into the pile pit 10, and reinforcements 13 are built in the bottomed cylindrical bag 12. Concrete 14 is placed in the bottomed cylindrical bag 12. When concrete is further placed in the bottomed cylindrical bag 12, the bottomed cylindrical bag 12 is expanded by concrete pressure and pushed against the pit wall of the pile pit 10, and a concrete pile, in which the pit projections of the pile pit 10 and the outer circumference of the bottomed cylindrical bag 12 are stuck fast and brought into contact, is prepared.