To facilitate a work for mounting an object to be supported or connection elements on a plurality of base structures, and to improve workability thereof.

A finished structure is constructed on a ground by: a plurality of base structures 10 each provided with two or more through-holes 12 through which piles 20 driven into the ground, the piles 20 respectively extending in different directions inclined with respect to a height direction without interfering each other, each of the through-holes having one end opened around a central part 11 on one side in the height direction and the other end opened on the other side in the height direction; and an object 40 to be supported arranged on one side in the height direction of the base structures. A method for constructing the finished structure includes: a first step of connecting the object to be supported or connection elements to the plurality of base structures 10; and a second step of inserting the piles through the through-holes of each of the base structures, respectively, and driving the piles into soil.