To provide a fixing method, by which a closed cell concrete board which has been often used as an exterior finishing material can be installed easily to a building frame body.

Closed cell concrete is molded, a metallic stationary plate is mounted on the rear of the concrete by a plurality of small-diametral nails generating strong holding power without generating cracks to the closed cell concrete, and the closed cell concrete board is set up to a building frame body by tapping screws. Plate thickness is thinned by a pressing machine or the like so that the small-dimensional nails are driven without bending in sections, where the small-diametral nails are driven, in the metallic stationary plate fitted onto the rear of the closed cell concrete at that time. On the other hand, sections fixed to the building frame body by the tapping screws in the metallic stationary plate are equalized to the thickness of various base materials so as not to weaken the bonding power of the tapping screws.