PURPOSE: To form a continuous wall without causing any damage to the adjacent structure by a method in which the first deep foundation is formed at a fixed interval, a preceding pile is erected in the foundation, the second deep foundation is formed, and then a following pile is erected.

CONSTITUTION: The first deep foundation 1 is excavated at a given interval, and preceding piles 12 are closely erected in the foundation 1a. The second deep foundation 1b is formed between the first deep foundations 1a, and following piles 15 are closely erected in the foundation 1b in such a way as to make it contact closely with the adjacent preceding pile 12. The underground continuous wall can thus be effectively constructed without causing any damage to the adjacent structure.