To provide a construction method for dissipating excess pore water pressure, which simply and surely prevents liquefaction of ground in a foundation section of an existing building.

This construction method comprises: a hole excavating step of excavating excavated holes (80t and 80) from the ground (G1) by using a machine (7) freely boring an area (G) below the building (T); and a pipe-like drain material installation step of arranging pipe-like drain materials (90 and 90C) in the excavated holes. A path (waterway 80) for releasing the excess pore water pressure in the area below the building to the ground side is composed of the excavated hole where the pipe-like drain material is installed. In the pipe-like drain material installation step, a sheath member (12), whose opening (12a) is formed on a surface, is inserted into the excavated hole, and the drain materials (90 and 90C) are arranged in the sheath member.