To reduce processes of wood working, economically manufacture a permanent form using wood, and freely change the size of the form according to need.

A steel pipe for a supporting frame 3 is installed in accordance with the slant of a surface of a structure, and base concrete is placed. A clamp 2 is installed in the supporting frame 3 through a hook part 21; and the wood 1 is supported on the supporting frame 3 and percussed from above, so that the clamp 2 can be driven into the wood 1. After that, the clamp 2 is driven into a top surface of the wood 1. A repetition of such operations makes pieces of the wood 1 stacked up to a required height, so at to complete the form. The form is formed by stacking the pieces of the wood 1 one by one, so that the size of the form can be finely adjusted by virtue of fluctuations in the number of the pieces of the wood 1. Recycled paper such as corrugated cardboard is fixed for lining to the backsides of the stacked pieces of the wood 1, so as to prevent leakage of the concrete.