Abstract: A free access floor comprising a plurlaity of units juxtaposed to both traversing and vertical direction, each unit comprising two right-angled triangular plates and first, second and third rectangular covers. Two triangular plates are so arranged to constitute a rectangle by facing their hypotenuses to each other. Two other side of each triangular plate have steps. Each triangular plate has three legs at its corners. The first, second and third rectangular covers are rested on the steps of the triangular plates. The triangular plate can be formed as a right-angled isosceles triangle, the first and the second rectangular covers can be formed as identical, and the third rectangular cover can be formed as a square. Each unit can be so arranged that the hypotenuses of the triangular plates of the adjacent unit are mirror symmetrical to each other. All legs gathering to the corners of each third rectangular cover can be grasped by each retainer.