PURPOSE: To promote the secureness of water resistance in addition to being lighter in weight and durable in quality by making a square inner frame with compressed cardboard after being stacked, crossing a horizontal plate to a relatively perpendicular vertical plate after its waterproofing, and constituting it from a corrugated cardboard paper-made buildup type grillwork reinforcer.

CONSTITUTION: At the time of forming a concrete foundation, a foldable section rectangular paper square cylinder 61 subjected to waterproofing is set up in a groove or the like forming its sidepiece at proper intervals. In this case, a square paper-made square inner frame 60 consisting of a corrugated cardboard paper-made buildup type paper grillwork reinforcer 65 being fitted in this square cylinder 61 is uprighted. Next, freshly mixed concrete is poured into a clearance between an inner surface of a groove or the like and an outer surface of this square inner frame 60 and, after being hardened, the square inner frame 60 is stripped off, whereby the concrete foundation with a hole, where an H-pole is inserted into, is completed. Subsequently the H-pole is inserted into the hole and, after additional fresh concrete is filled up in a gap between the pole and the hole inner surface and after being hardened, the H-pole is locked tight. With this constitution, in time of the fresh concrete pouring thereinto, any pressure of the fresh concrete is prevented from occurring, so any possible deformation is preventable.