To form a satisfactory crushed stone pile of which the supporting power is improved with the weak ground.

An object ground (g) is dug by rotary drilling means 5 and on a generated drilling hole 11, a cylindrical casing 6 is disposed of which the diameter is larger than that of the drilling hole 11. A vibrating pressure is applied to the casing and while generating a liquefaction phenomenon in the surrounding ground (g), the casing is press-fitted into the ground (g). Thereafter, the cylindrical casing 6 is lifted up, and crushed stones are thrown from a crushed stone throwing port 6b in a lower end into a pile hole 12 under the casing. Next, the crushed stone throwing port 6b is closed, a vibrating pressure is then applied through the cylindrical casing 6 to the thrown-in crushed stones and while further generating the liquefaction phenomenon in the surrounding ground, the thrown-in crushed stones are compacted. Then, a cycle from lifting up the cylindrical casing 6 to completing the compaction is repeated until completing the cycle over an entire range in a height direction of the pile hole 12. Thereafter, the surrounding ground (g) which subsides because of the liquefaction phenomenon is embanked.