To provide a heat insulating waterproof structure and a heat insulating and waterproofing method for a structure using a resin foam with excellent heat resistance.

The heat insulating waterproof structure 1 is formed by laminating at least a heat insulating material 5 and an asphalt roofing sheet 7 on a backing surface 2 of the structure. The asphalt roofing sheet 7 has an adhesive asphalt layer at least on the back face side. The heat insulating material 5 is formed by foaming a resin composition containing a copolymer (A) consisting of an aromatic vinyl unit, an unsaturated dicarboxylic acid anhydride unit and an N-alkyl-substituted maleimide unit, and a copolymer (B) consisting of the aromatic vinyl unit and a vinyl cyanide unit. The adhesive asphalt layer is fused by heating to fuse the asphalt roofing sheet 7 to the upper side of the heat insulating material 5.