To cope scales of columns, beams and the foundation with a foundation of wooden-construction and to achieve construction even on a land with a poor bearing force since a mixed-construction design enables to build the mixed construction provided with rigid-frame of wood, steel or reinforced concrete of a necessary number in a necessary places of a long distance or a large space in a framework part of each layer of a wooden-framework construction method or a two-by-four construction method, so that there is no need of building the lower structure entirely in a steel-framed or a reinforced-concrete structure and that a floor-framing of the wooden-framework construction method or the two-by-four construction method can be used with less dead weight of a heavy floor and less load to columns or beams.

Using a calculation method for the mixed construction based on the wooden-framework construction method, the two-by-four construction method at each layer and the rigid-frame method, a rigid-frame stress of the wooden-framework, the steel-framework and the reinforced-concrete structure is analyzed into a wall magnification, and the building is designed by calculating under calculation methods for an allowable unit stress design or the like of the wooden-construction according to the wall magnification and a limit strength calculation together with the wooden-framework construction method and the two-by-four construction method.