PURPOSE: To control snow thickness in an indoor skiing ground easily at a low cost by putting out indoor lights before arranging a slope, lighting floor light sin the slope to visually confirm a snow layer transmitted light, snowing to a bright part, and moving snow in a dark part to maintain snow thickness in specific value.

CONSTITUTION: A floor screen 10 is formed of a heat insulating material layer 11 and a floor material layer 12 of concrete mortar. After that, a floor light 15 is stored in a recession 13 of the floor material layer 12. An opening of the recession 13 is covered with a reinforced glass sheet 14 to seal. In the case of installation, lighting is put out to light the floor light 15. Then, a thin part of a snow layer A is lightened by a snow layer transmitted light, and the thick part is darkened to easily visually confirm snow thickness. Accordingly, snowing is made in a thin part by a snow making machine, and surface snow in the thick part is moved to the thin part by an equipment car. The entire transmitted light B has the same extent of brightness. According to the constitution, the maintenance and control of a snow layer can be made easily at a low cost.