To provide a heat insulating and waterproofing technique wherein a heat insulating material is not melted or deformed with heat during the thermal fusion bonding of waterproof sheets even when a polystyrene foam is used as the heat insulating material, and a heat shielding member can be arranged in a very limited range for sufficiently shielding heat.

In the heat insulating and waterproofing technique, the waterproof sheets 3 are mechanically fixed and placed onto a bed 1 via a heat insulating layer 2, where the waterproof sheets 3 are bonded to each other with thermal fusion bonding. The polystyrene foam is used as the heat insulating layer 2, and a bonded portion between the waterproof sheets 3 includes the heat insulating member 4 laid between the waterproof sheet 3 and the heat insulating layer 2.