To convert light into a chemical substance with high conversion efficiency. A device, comprising: a photovoltaic layer having a first face and a second face; an oxidation electrode layer electrically connected to the first face of the photovoltaic layer; a reduction electrode layer electrically connected to the second face of the photovoltaic layer; a first electrolytic solution being supplied to the oxidation electrode layer; a second electrolytic solution being supplied to the reduction electrode layer; and a porous layer, provided to in contact with at least one of the first electrolytic solution and the second electrolytic solution, having fine pores through which a product produced by the oxidation reaction or the reduction reaction passes, and being given a temperature gradient wherein the product being purified by the porous layer.
