To provide a burying structure of an underground heat exchanger capable of dramatically improving heat exchanging effectiveness between the underground heat exchanger and the earth, expanding a range of the earth for utilizing geothermal heat by collecting heat from the ground and radiating heat into the ground, dramatically improving geothermal heat utilizing efficiency, and securing the necessary heat exchanging quantity without making a vertical cave deep and increasing the number of vertical caves, thus the elongation of term of works and the increase of construction costs can be prevented, and the construction workability can be improved.

In this burying structure of the underground heat exchanger comprising the vertical cave 101 formed in the earth 100, the underground heat exchanger 2 disposed in the vertical cave 101, and a filler 102 filled in the vertical cave 101, the filler 102 includes silicon particle of purity of 90% or more.