The bottom structure of the tower

[PROBLEMS] To provide a bottom structure of a steel tower capable of reducing the load stress imposed on a newly-founded foundation and main pillar material and the existing foundation and main pillar material, and capable of rebuilding work in an existing site. Objective. In a bottom structure of a steel tower to be rebuilt in response to an increase in capacity of a steel tower, a plurality of new foundations 4A to 4D are installed on a structural surface 3 connecting the existing foundations 2A to 2D. These new foundations and existing main pillars are connected by reinforcing members 5 and 6 so that the foundation stress is shared between the existing foundation 2 and the new foundation 4. It is possible to bear at least all of the additional stress accompanying capacity increase with the new foundation 4, and the upper member only needs to reinforce the lowermost section, and does not reinforce the existing foundation. And low cost. In addition, the new member can be installed in the existing construction surface, and the land cost does not increase and is inexpensive. [Selection] Figure 1