To provide a new nano-structural material that has pores of regular, several tens nm size and also exhibits high thermal stability, and to provide its preparation method.

Provided is a preparation method of a nano-structural material which is a structural body having a micro phase separation structure formed by a block copolymer which bonds two or more polymer chains incompatible with each other and having silicon for the polymer to form one separation phase of the micro phase separation structure and which method selectively removes, by heating the structural body, the polymer chains not having silicon to form vacancy.