PURPOSE: To prevent the occurrence of floating or unequal settling and execute the construction work in a short construction period and at a low cost.

CONSTITUTION: A reinforcing bar basket 3 is placed into an excavation groove 3 and concrete is cast there so that an underground continuous wall main body 4 is constructed. Not only reinforcing bars 3a are added to the reinforcing bar basket 3 but also pipes 5 are further installed vertically in a specified number of rows. The ground further below the bottom of the excavation groove 2 is excavated with a jet bolt by way of the pipes 5 so that it reaches a support ground E1 at a depth layer, thereby ejecting mortar from the pips of he pipes and building an anchor 7 on the support ground. The lower end of this jet bolt 6 is fixed with the anchor 7 while mortar is filled up into the pipes 5. Then, the upper end of the jet bolt is fastened with a nut 9 and anchored with the top of the underground continuous wall main body 4 after the concrete is cured. Then, tension is applied to the jet bolt 6, thereby using this as a tensile material.