To give deodorizing effects of woody carbide, mildewproof effects by humidity conditioning, and minus ion effects to a building board by providing a woody char layer on a woody board as the building board.

The woody char layer 3 is formed on a middle layer or the lower surface of the woody board as the building board from the side end of the woody board 2 up to a side end facing the woody board 2 using powdery or granular woody carbide 3A and at least a part of the woody char layer 3 is exposed to the outside. This building board can be applied to any of floor materials, wall materials or ceiling materials.