To provide a construction method which materializes considerably easy and low-cost construction of geothermal power generating facilities.

In the construction method, a vertical hole 5 is excavated in the ground G by replacing an adapter of heavy equipment 2 with an auger 4 after burying steel pipe piles 1, 1 in the ground G by employing the heavy equipment 2. U-shaped pipes 10, 10, 10, 10 are embedded in the excavated vertical hole. After that, the embedded U-shaped pipes 10, 10, 10, 10 are connected one another so as to form a series of pipes P. After forming a base 8 of a building so as to be stretched between the embedded steel pipe piles 1, 1, 1, the building 9 is built on the base 8, and a heat pump 11 is mounted inside a building 9. By connecting the heat pump 11 with a series of pipes P, the construction of the geothermal power generating facility is executed.