A proton conductor mainly contains a carbonaceous material derivative, such
as, a fullerene derivative, a carbon cluster derivative, or a tubular
carbonaceous material derivative in which groups capable of transferring
protons, for example, --OH groups or --OSO.sub.3 H groups are introduced
to carbon atoms of the carbonaceous material derivative. The proton
conductor is produced typically by compacting a powder of the carbonaceous
material derivative. The proton conductor is usable, even in a dry state,
in a wide temperature range including ordinary temperature. In particular,
the proton conductor mainly containing the carbon cluster derivative is
advantageous in increasing the strength and extending the selection range
of raw materials. An electrochemical device, such as, a fuel cell, that
employs the proton conductor is not limited by atmospheric conditions and
can be of a small and simple construction. The proton conductor may
contain a polymer in addition to the carbonaceous material derivative,
which conductor can be formed, typically by extrusion molding, into a thin
film having a large strength, a high gas permeation preventive ability,
and a good proton conductivity.
