PURPOSE: To apply the method even for execution of a foundation pile of small diameter, and provide large supporting force and resisting force against drawing out.

CONSTITUTION: A cylindrical foundation pile main body 1 is mounted to a rotation device 12, and the pile main body 1 is press-fitted up to prescribed depth (a) while normally rotating. At this time, if necessary, air is jetted from the nozzle of a force feed pipe 5 inserted in the pile main body 1, so as to reduce wall friction between the inner wall of the pile main body 1 and inner earth and sand. At reaching the prescribed depth (a), the pile main body 1 is reversely rotated so as to open spread blades 3 and perform spread drilling. Foot protective material 14 is Jetted through the force feed pipe 5. By hardening of the foot protective material 14 stirred and mixed with earth and sand by means of the spread blades 3, a spread foot protection part 15 in which the spread blades 3 in the opened condition is used both as an anchor and reinforcing material, is completed.