To make it possible to construct a tension member easily and definitely in the case when an underground skeleton, such as a basement is constructed in a pile construction method which buries a tension member in cast-in-place concrete and eliminate the construction work of a tension member in pile construction work and troublesome problems of the work and enhance workability.

In the case when an underground skeleton, on which a heath pipe 3 is mounted only in a foundation of the underground skeleton, is constructed, a reinforcing bar cage 2 is placed in the lower part of an excavation hole 1 excavated from the ground. After concrete 4 is cast only in an area which is the foundation of the underground skeleton, an evacuated area in the excavated hole 1 is backfilled with sand 6 and the underground area is excavated and the heat of a pile is exposed and a tension member is inserted into the sheath pipe 3 and strained.