Abstract: A body reinforcing material arrangement structure, comprising reinforcing materials disposed in a car structure formed by the combination of the panels forming the body of a car or in the body, the reinforcing material further comprising a platy support body having a portion disposed apart a specified distance from the panel along the internal surface of the panel at least partially and a resin formed body having heat-foaming capability disposed between the portions of the platy support body disposed along the panel and the panel, wherein the resin formed body is so disposed as to be supported on the platy support body before foaming, positioned apart a clearance from the inner surface of the panel, and after forming, filled between the platy support body and the panel so as to be fitted to the panel.