To provide an insole provided with a radiation protection function and having high foot comfort and flexibility, and a material.

A mechanical alloying structure 3 formed into a powdery shape by perfectly covering individual metal fine particles 9 with a polymer material 10 includes: the metal fine particles of heavy metals of W, Zn, Bi, Pb, Sn, Sb, Cu and Ni, the oxide thereof, the carbide thereof or the like having a diameter of 100 nm to 300 μm and having the shielding properties of radiation; and a polymer material such as thermosoftening nylon, polyethylene, polyvinyl chloride, polystyrene, polycaprolactone (PCL), polybutylene succinate (PBS) and polylactic acid which are capable of mechanical alloying with the metal fine particles. The respective mechanical alloying structures are arranged in a multilayer in a composite manner into a mechanical alloying material 2. The mechanical alloying material 2 is subjected to compression molding and is formed into a sheet shape, is cut into the shape of an insole 1 of shoes, and is formed into a desired shape such as a flexible sheet material having the properties of metal in appearance and in characteristics though its outside is made of plastic.