To lighten and strengthen a reinforcing tool for reinforcing a crossing part and a joining part of a column and a beam of a wooden building of a framework structure.

This reinforcing tool 1 of the building reinforces the crossing part and the joining part of the column and the beam of the building. The reinforcing tool 1 is formed by integrally projecting a reinforcing flange 3 to both sides of its reinforcing tool body 2 as a lightweight material of FRP, FMP, ceramics and light metal such as an aluminum alloy and a titanium alloy. The reinforcing tool 1 can be joined without generating a cavity in the joining part by an adhesive when joined to the building by arranging a recess-projection part on the reverse surface side, and arranging a swelling part of swelling the central side a little along the axis of the reinforcing tool body on this reverse surface side, and can open a belt fixing opening 4 for binding and fixing a belt-like belt fixture 5 to the column and the beam to the flange 3 projected on both sides of the reinforcing tool body 2.