To improve underfloor ventilation performance without damaging the strength of a foundation, and to simply correspond to various building arrangement.

In the foundation structure of a building having the first foundation section 21 rising along the contours of living room sections 11A to 14A for the building 100 while having the second foundation section 22 rising along the contours of garages 13B and 14B as being connected to the first foundation section 21, a columnar foundation 23 on which the building is placed is installed on the inside surrounded by the first foundation section 21.