To make it possible to form a complex ground having a support force in conformity with an overburden load in a short construction period and at a low cost and minimize an influence against a peripheral ground.

A proper amount of porous materials, such as a cellular material or a foam bead, for example, light weight aggregates including a large number of foams are mixed with a soft original ground 11 and a curing material, such as cement is added thereto so that the ground may be solidified, thereby forming a light weight supporting body whose unit cubic weight is smaller than that of the original ground 11. An upper reinforced ground 13 is integrally formed on this light weight supporting body 12, thereby constructing a structure, such as an embankment main body on this upper reinforced ground 13.