To control the radio wave absorption performance easily without causing the problems of weight burden to a building and workability.

After arranging multiple pieces of urethane foam resin 22 in stripe at positions on the surface of a metal frame 1 while ensuring predetermined intervals, a curable liquid radio wave absorbing material 21 is applied between the pieces of urethane foam resin 22. Thereafter, the urethane foam resin 22 is removed and a weatherproof overcoat material, i.e. a polyurethane resin material, is applied to the surface of the radio wave absorbing material 21 and between the radio wave absorbing materials 21 thus providing a radio wave absorption layer 20 where the radio wave absorbing materials 21 are arranged in stripe on the surface of the metal frame 1 while spaced apart from each other.