PURPOSE: To exclude the electromagnetic wave and to prevent the malfunction due to the electromagnetic wave by surface-treating the construction-industry product consisting of an inorg. material such as roof tile and ceramic with the extract of a specified plant.

CONSTITUTION: The construction-industry product consisting of an inorg. material such as roof, tile, brick and ceramic is surfacetreated with the extract of the plant such as wood, bamboo, algae-and seaweeds to exclude the electromagnetic wave. Otherwise, the material is surface-treated with the fine powder of the plant or the fine powder of the carbonized plant to form a surface- treating layer. Further, an additive consisting of a metal or a soln. of the metal is added to the extract, fine powder, liquefied material, etc., of the plant, and the product is effectively surfacetreated with the admixture.