PURPOSE: To exactly form construction pits in parallel with piles by a method in which a guide part rotatably supported on an auger screw shaft is coupled with the outside coupling portion of the preceding steel tubular pile, and excavation is made by the auger.

CONSTITUTION: The first construction pit is excavated by an usual method, and the first steel tubular pile (a) is erected into the construction pit by an usual method. The vertical guide 8a of a gide part 8 rotatably supported by an auger screw shaft 7 is fitted into a coupling portion (b) on the female side of the steel tubular pile (a), and excavation is started by operating the auger. Since the auger screw 6 gradually penetrates downwards into the ground but the shaft 7 is guided by the guide part 8, the construction pits in parallel with piles (a) can be exactly excavated. The next steel tubular pile (a') is coupled with coupling portions (b) and (c') and erected into the construction pit. These processes are repeated to construct a steel tubular pile underground wall.