PURPOSE: To shorten the working time by forming a concrete placing form for the footing part from undulate sheet, thin plastic sheet, etc., and burying underground together with the concrete placed in the form.

CONSTITUTION: In the longitudinal direction of a body part 2, a base frame 1 having a plurality of reinforcing ribs 5 is formed, which is made of metal sheet or plastic sheet. Such base frames 1 are installed facing one another, and an anchor 7 is driven into each hole 6 in a mounting piece 4, and soil is put over outside of the body 2. Then a rising frame 8 is placed on the horizontal part 3 at the top of the base frame 1 and mounted. Reinforcing steel bars are arranged in this rising frame 8 and the base frame 1, and concrete is placed and hardened. Only the rising frame 8 is removed, and soil is filled back over in the condition with the base frame 1 left as it is.