PURPOSE: To facilitate accurate construction of column even for an unskilled worker by forming a major assembly column mold into a concrete casting condition, or into a condition where the mold can be extracted from a column construction part through a positioning adjustment of an opening/closing nut.

CONSTITUTION: A major assembly column mold F is formed out of a pair of veneer plywoods and a pair of veneer plywoods 2, while a hold is formed on the end parts opposed each other of the veneer plywood 2, so as to install an opening/closing bolt 3 in it, and the distance between the opposed surfaces of the veneer plywoods 2 can be adjusted by an opening/closing nut 4. The distance of the opposed surfaces of the veneer plywoods 2 is narrowed and concrete is cast in the assembled major assembly column mold F so as to construct a column, while the distance between the opposed surfaces is widened, and the major assembly column mold F is thus extracted from a column construction part to the upward.