PURPOSE: To prevent the freezing of the foundation ground of an artificial skiing ground by installing vent pipe laying layers between piping laying layers for cooling and the foundation ground forming the under-floor structure of a slope, thereby forming air layers.

CONSTITUTION: Cloth foundations 51 are built on the sloped foundation ground 50 of the artificial skiing ground. Crushed stone laying layers 21 and asphalt concrete layers 22 are then formed and, thereafter, the vent pipe laying layers 23 are formed by perforated precast concrete blocks. Heat insulating panel layers 54 consisting of foamed polyethylene, etc., and cooling pipings 55 are laid to form ice layers 56. Further, the vent pipes of the vent pipe laying layers 23 are laid by providing these pipes with differences in height in the under-floor structure of the slope to allow natural ventilation of the cold air from the cooling pipings 55. The waste heat subjected to a heat exchange by a refrigerator is passed through the vent pipes to increase a ventilation rate and to prevent the temp. fall of the foundation ground 50.