To provide a underfloor ground heat utilizing natural heating method of a house, capable of further effectively maintaining the temperature of a dwelling space of the winter season at the comfortable temperature more than invention of a patent document 1.

Warm air warmed by solar heat in first clearance for closing the periphery between a glass panel arranged outdoors and receiving the sunlight and a perforated metallic plate opposed to the glass panel, is sucked via the perforated metallic plate in second clearance for closing the periphery between a backing panel opposed to the perforated metallic panel and the perforated metallic panel. The warm air in the second clearance is returned to the first clearance via a pipe arranged on a dirt floor concrete surface or arranged in the vicinity of the dirt floor concrete surface in a state of burying a part or a great part in dirt floor concrete in a cross-sectional view and a pipe connected to the pipe in the winter season from the autumn season; and is returned to the first clearance via a pipe arranged a floor backing or concrete placed in the floor backing and a pipe connected to the pipe in early autumn from the summer season.