PURPOSE: To shorten the construction period by integrally forming a partition body by concrete at the time of concreting outer wall and an upper story slab while providing a steel-inserting cavity part in a vertical direction in the multistory building partition body constructed in each story.

CONSTITUTION: A cylindrical cavity part 2 into which a steel bar 3 is vertically inserted is provided in a partition wall body 1. Next, the partition wall body 1 is vertically provided on an existing slab 40 and its upper end 1a is protruded inside a horizontal sheathing board 6. Its side end is similarly protruded inside a vertical sheathing board. The steel bar 3 is inserted into the cavity part 2, which is also filled with concrete simultaneously with the casting of concrete in an outer wall and an upper story slab 50. In this way, the working efficiency can be improved.