Abstract: Disclosed is a proton conductor which does not need to replenish water and which can be used even in a dry atmosphere and in a high temperature range. The proton conductor includes carbon clusters having functional groups capable of releasing a proton, and a substance having portions capable of serving as proton-receiving portions. Alternatively, the proton conductor includes a substance having functional groups capable of releasing a proton, and carbon clusters having portions capable of serving as proton-receiving portions. Carbon clusters, particularly, those carbon clusters which have a specified molecular structure such as fullerenes and carbon nanotubes, with various acid functional groups introduced thereinto, show proton conductivity even in a dry state, and an addition of a substance for promoting the dissociation of protons to the carbon clusters enhances the proton conductivity drastically.