To prevent the deformation and damage of a building even when large force in the horizontal direction is applied to the building by an earthquake, etc.

In a wooden building, frame bodies 13 for installing ceiling panels manufactured by assembling rail materials 15, 16 and frame bodies 14 for mounting floor panels manufactured by assembling rail materials 17, 18 are placed among mutually parallel horizontal members 11, 11 such as beams, and fixed onto the horizontal members 11, 11. The floor panels 32 are fixed onto the top faces of the frame bodies 14, the ceiling panels 31 are fastened onto the undersides of the frame bodies 13, and rigid reinforcing plates are placed and fixed onto the top faces of the frame bodies 13 while both sides of the rigid reinforcing plates parallel with the horizontal members 11, 11 are brought near and fastened onto the horizontal members 11, 11.