To provide a heat-insulating and waterproofing structure by which heat-insulating performance is improved at a low cost by using a hard polystyrene foam as a heat-insulating layer in the heat-insulating and waterproofing structure, and the heat insulating layer is prevented from being damaged even when a person walks on a waterproof sheet or a shock is applied.

In the heat-insulating and waterproofing method, the heat-insulating layer 2 is arranged on an underlayer 1, and the waterproof sheet 3 is laid on it. The polystyrene foam is used as a material for the heat-insulting layer 2, and a soft cushioning material 4 is arranged between the heat-insulating layer 2 and the waterproof sheet 3.