PURPOSE: To prevent the settlement of a building when constructing a large self-weight building, such as a multistoried building on a soft ground.

CONSTITUTION: A mat foundation 3 is cast on a soft ground 1 where a plurality units of weights 6, which are equivalent to the weight of a building structure scheduled to be erected, are loaded on the mat foundation 3. While the building structure 5 is being constructed on the mat foundation 5, the weights 6 whose units are equivalent to the weight of the building structure on the way to construction in each construction stage are removed from the mat foundation 3. All the weights 6 are removed when the construction of the building structure is completed.