To eliminate the limitation of the size of the board of a stepped base, to compactly house the board, and to enable the use as a two-step or more base by combining one-step boards.

This board has hollowed legs directly mounted thereon, and the number of legs is increased according to the size of the board. The legs are arranged so that thin legs can be regularly superposed on thick legs and inserted to the hollow parts of the thick legs when the bottom faces of the boards are allowed to abut on each other. The board has a plurality of holes extending through the legs and the board so that the board can be used in piles. The boards are piled so that the holes are linearly arranged, and bars are inserted to these holes, whereby a plurality of boards are vertically fixed.