[PROBLEMS] To provide a structure capable of easily switching between turf and a floor in a short period in a natural turf facility. SOLUTION: A plurality of pillars are disposed at a base portion of the competition area, and the pillars can be exposed by removing natural grass and soil cultivation immediately above the pillars, and for pillar fixing. And a lid for separating the bolt structure from natural grass and soil consolidation, and the pillar erected portion is provided with a pillar having a predetermined height or more than the surface of the natural grass after installation. Adopt a means of passing beams between columns, placing a floor on the beams, and covering the playing area with the floor. [Selected figure] Figure 1【課題】天然芝施設において、短期間で、容易に、芝と床を切り替えられることが可能な構造を提供する。【解決手段】競技領域の基礎部分に柱立設部が複数配置され、柱立設部は、柱立設部の直上の天然芝及び養土を除くことで、露出可能であり、柱固定用のボルト構造と、ボルト構造を天然芝及び養土から隔離するための蓋と、を備え、柱立設部には、設置後天然芝の面よりも所定の高さ以上となる柱を設置し、複数の柱の間に梁を渡し、梁の上に床を設置し、床によって競技領域を覆うという手段を採用する。【選択図】図１
