PURPOSE:To prevent separation of a slope form material, by a method wherein a holed pipe pile having through-holes is inserted through a hole in a joint for driving, and after the slope from materials are assembled as the opening of the joint is secured by means of a metal fitting, concrete is placed in the slope forms. CONSTITUTION:A slope form material 1 is inserted in joints 2, and a holed pipe pile 6, having through-holes 7, is inserted through a hole formed in the bottom of the joint 2, and is driven for securing in a manner that the head part of the pile remains at the interior of the joint 2. The slope form materials 1 are assembled on a face 30 of slope as the opening of the joint 2 is closed and secured by a metal fitting 5 by means of a bolt 3 and a nut 2. When concrete is poured from the upper part of the slope form materials 1, the concrete flowns down the interior of the slope materials 1, the interior of the slope form material is filled from the lower part with the concrete, and the concrete is further poured through the head opening part of the holed pipe pile 6 to fill the interior of the pile therewith. The air in the pile 6 is bled through the through-holes 7, and gaps in soil are filled with mortar mill 7 percolated through the through-holes 7.