To provide a lightweight, non-combustible building board which provides a comfortable interior space by decomposing and removing VOC released from building materials, preventing molds, mites and dew-drops through its humidity-controlling action and effectively eliminating the problems of sick house syndrome, etc., through emission of negative ions or far-infrared rays.

A mixture is obtained by mixing 10-30 wt.% granular tourmaline ore, 30-50 wt.% diatomite, 30-50 wt.% pearlite, 5-20 wt.% activated carbon, 20-50 wt.% solidification agent (cement or gypsum) and optimum amounts of solidification auxiliary (such as vinyl acetate and sodium silicate) and water, press-molded into a shape of a board and dried by heating, thus forming pores on its surface.