PURPOSE: To improve fire protective performance by sticking surface plates on each of which a noncombustible projected board made by filling or fixing noncombustible inorganic compounds in the cellar holes and/or on the inner wall surfaces has been stuck, on the surfaces of a framed core material.

CONSTITUTION: Noncombustible inorganic compounds are filled in the void parts such as cellar holes of a projected board consisting of dried wood, or noncombustible inorganic compounds are fixed or stuck in layers along the inner walls of cellar holes, and further noncombustible inorganic compounds are fixed or stuck even on the front and rear surfaces of the projected board for performing non-combustible treatment. And the projected board having been made noncombustible is stuck on a base plate via an adhesive substance in which noncombustible inorganic compounds have been mixed, to form a surface plate. Then, the surface plates are stuck on the front and rear of a framed core material via an adhesive substance in which noncombustible inorganic compounds have been mixed. Thus, fire protective performance can be improved.