PURPOSE: To improve safety by annexing a jack at a front end, executing a friction cut to the peripheral surface of a pile, constructing an underground pile and lowering a ground structure by the jacking down of the front end of the pile only by quantity corresponding to land subsidence.

CONSTITUTION: A jack 1 is installed beforehand at the front end of a pile, and a friction cut 15 is carried out on the peripheral surface of the pile, thus constructing an underground pile 2. The jacking-up of the jack 1 is conducted at a stage when the strength of the pile 2 appears, and the height of the pile heads of each underground pile 2 is levelled. A ground structure 3 is built on the pile 2, and the jacking-down of the front end of the pile is performed only by quantity corresponding to the clearance S of a ground level 4a generated by land subsidence after completion and a foundation batholith 3a. The structure 3 is lowered, level difference is removed, and the jack 1 is fixed under a passive state. Accordingly, the generation of excessive stress in the head section of the pile is prevented, thus improving safety.