Calcination of an alternating ruthenium-S-phenylene hybrid copolymer under an argon atmosphere was found to give nano-sized ruthenium sulfide/carbon cluster composite material. ESR spectral examinations of the material revealed that an electron transfer from ruthenium sulfide particles to carbon clusters took place to raise a visible-light responsive oxidation-reduction function with an oxidation site at ruthenium sulfide particles and a reduction site at carbon clusters. The surface of the calcined material was modified with Pt particles, and the reduction ability of the resulting modified material was examined.