A hydrogen ionic conductive inorganic material having a layered structure, wherein a moiety containing a functional group with hydrogen ionic conductivity is introduced between layers of an inorganic material having a nano-sized interlayer distance. A polymer nanocomposite membrane including a reaction product of the hydrogen ionic conductive inorganic material and a conductive polymer, and a fuel cell using the same, are also provided. In the polymer nanocomposite membrane, a conductive polymer may be intercalated to a hydrogen ionic conductive inorganic material having a layered structure or products exfoliated from an inorganic material having a layered structure are dispersed in a conductive polymer.