PURPOSE: To perform the construction of clustered stone simply by a method in which a clustered stone-forming space is formed between the formwaoks of paired formwark holding plates in a clustered stone formwork device for foundation work and then concrete is placed into the space.

CONSTITUTION: A nut 19 is screwed from the upper part of the lower piece 1b of a support body 1 into the upper part of a support pile 12 and clamped to fix the support body 1. The groove 20 of a formwork holding plate 4 is fitted on a bolt 5 piercing through the long hole 2 of the upper piece 1a of the support body 1, and paired formwork holding plates 4 are laid between the support bodies 1. The formwork holding plates 4 are moved along the longitudinal direction of the support body 1, the formworks are adjusted so as to arrange each of the formworks every designated clustered stone pitch, and the nut 6 is clamped. When placing a stone foundation 7, concrete or mortar is filled in a space for forming clustered stone inside the formworks 3 and allowed to stand. After hardening, the formworks 3 are removed and the support body 1 and the support pile 12 are also removed.