To reduce excavated surplus soil, and integrate a bearing pile with concrete.

In a first process, when a pile hole 20 with a large-diameter hole bottom part 20A is excavated, the excavated surplus soil G is generated. In a second process, the concrete C is placed on the expanded hole bottom part 20A. Then, in a third process, a steel pipe 21 is made to descend into the pile hole 20, and a lower part 22A of the steel pile 21 is embedded in the placed concrete C. Spiral ribs 23, which are radially protruded from inner and outer peripheral surfaces, are formed in the lower part 22A. The concrete C is placed on the bottom part 20A, and the lower part 22A is embedded in the placed concrete C so that foot protection can be performed. After that, in a fourth process, the inside of the pile hole 20 is backfilled with the surplus soil G so that a foundation pile can be constructed.