To execute a subsurface construction such as a water storage tank safely and surely in a short time by interrupting groundwater, and to reduce construction cost.

An impervious wall 5 is built so as to completely surround a section to be dug down in a ground in the peripheral direction prior to the digging-down of the ground and the burying of the construction 2 under the ground. The impervious wall 5 is formed by continuing soil cement-like columnar articles 6 in the peripheral direction in arrangement, in which the side sections of the columnar articles 6 are overlapped mutually. The impervious wall 5 built in this manner is left in the ground even after the construction 2 is buried under the ground.