PURPOSE: To promote high efficiency and simplification of work to reduce a construction period, and uniform finished goods without relying on skilled technicians and execute high quality of flooring of house building.

CONSTITUTION: In a wooden framework building forming a framework (b) by connecting plumb members 3 such as columns, etc., the foundation, girders or beams and cross members such as horizontal members, etc., it is so formed that side edges or intermediate sections can be fitted to the plumb members 3 in the framework (b). Floor panels 4 formed by holding cores 5 between faces 6 and 7 on both sides are spread on the cross members 2. Accordingly, construction period can be greatly reduced and, at the same time, construction can be carried out at a low cost, the floor panels 4 accompanied with the face members 6 and 7 on both sides of the cores 5 are used for construction of a floor, so that even if it is simple constitution, a load bearing floor exceeding the standard is formed, the load bearing floor excellent in the heat insulating effect and the soundproof effect is obtained and, at the same time, in walking, etc., during the work, free movement can be made on the floor panels 4, so safe work is carried out.