A building board comprising: a base material; a sealer layer formed on the surface of the base material; an insulating coating film formed on the sealer layer of the base material for covering a surface of the base material; and a transparent clear coating film for covering the insulating coating film, wherein the insulating coating film has an average film thickness of 5 to 50 μm, and contains a coating film forming material, organic hollow particles, and a water-soluble solvent, and the insulating coating film contains 0.01 to 5.0 parts by mass of the organic hollow particles with respect to 100 parts by mass of solid content thereof, and the organic hollow particles have an average porosity of 80% or more and an average particle diameter of 5 to 50 μm, and comprise at least one of acrylonitrile, methacrylonitrile, vinylidene chloride, acrylic ester, and styrene, and the water-soluble solvent is at least one of a glycol-based solvent and a glycol ether-based solvent, the boiling point of the water-soluble solvent is higher than the temperature of the coating film when the coating film is dried in the step of forming the insulating coating film and the step of forming the transparent clear coating film, the content of the water-soluble solvent is 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid content of the insulating coating film, and wherein the transparent clear coating film is constituted by any water-soluble paint selected from a group consisting of acrylic silicone resin emulsion paint, acrylic resin emulsion paint, silicone resin-based paint, acrylic urethane-based paint, fluororesin-based paint, and polyurethane resin-based paint, a base material; a sealer layer formed on the surface of the base material; an insulating coating film formed on the sealer layer of the base material for covering a surface of the base material; and a transparent clear coating film for covering the insulating coating film, wherein the insulating coating film has an average film thickness of 5 to 50 μm, and contains a coating film forming material, organic hollow particles, and a water-soluble solvent, and the insulating coating film contains 0.01 to 5.0 parts by mass of the organic hollow particles with respect to 100 parts by mass of solid content thereof, and the organic hollow particles have an average porosity of 80% or more and an average particle diameter of 5 to 50 μm, and comprise at least one of acrylonitrile, methacrylonitrile, vinylidene chloride, acrylic ester, and styrene, and the water-soluble solvent is at least one of a glycol-based solvent and a glycol ether-based solvent, the boiling point of the water-soluble solvent is higher than the temperature of the coating film when the coating film is dried in the step of forming the insulating coating film and the step of forming the transparent clear coating film, the content of the water-soluble solvent is 0.1 to 10 parts by mass with respect to 100 parts by mass of the solid content of the insulating coating film, and wherein the transparent clear coating film is constituted by any water-soluble paint selected from a group consisting of acrylic silicone resin emulsion paint, acrylic resin emulsion paint, silicone resin-based paint, acrylic urethane-based paint, fluororesin-based paint, and polyurethane resin-based paint,