PURPOSE: To cover not only the surface of a noncombustible board but also the entire side surfaces thereof with a noncombustible film, and further to prevent the separation of the noncombustible film.

CONSTITUTION: A noncombustible film 12 is placed on the surface 1a (not shown) of a noncombustible board 10, and is pressedly brought into contact with the side surfaces 2, 3 (not shown) of the board, and further the end parts thereof are turned around so as to be pressedly brought into contact with the rear 6, 7 (not shown) of the side surfaces. The edge parts 18 are pressedly brought into contact with the ends 4, 5 (not shown), and from above thereof flap parts 20 are pressedly brought into contact with the but ends 4, 5 and further with the rear 8, 9 (not shown) of the ends. Thus, a noncombustible decorative board that is fine and has a feeling of high-grade can be obtained. In addition, the separation of the film can be prevented and durability can be enhanced.