A method of manufacturing a supporting structure includes disposing a supported member between a pair of support walls opposed to each other, the support walls and the supported member having through shaft holes formed coaxially through the support walls and the supported member respectively, inserting a shaft member through the shaft holes in the disposed state, the shaft member has two ends each of which has a peripheral portion circumferentially divided into a plurality of swaging portions, and swaging the swaging portions sequentially such that regions of the shaft member corresponding to the respective swaging portions are fixed in the shaft holes of the respective support walls.