To attain efficient systemization of a solid polymer fuel cell and hydrogen production unit and to provide a solid polymer fuel cell system, enabling the use of a fuel cell exhaust gas as a high-purity hydrogen for hydrodesulfurization.

An exhaust gas j (hydrogen for hydrogenate desulfurization) is added to hydrocarbon a, and thereafter the sulfur content is desulfurized in the hydrodesulfurizer 11. Desulfurized hydrocarbon c is steam-reformed in the steam reformer 12, to generate a high concentration hydrogen-containing gas d. The gas d is then sent to a gas modifier 13, to convert carbon monoxide to carbon dioxide and hydrogen, and a high concentration hydrogen-containing gas e after the gas modifier 13 is supplied to a PSA Section 14 to refine high- purity hydrogen. Then, refined high-purity hydrogen h is moisture-adjusted and sent to the solid-polymer fuel cell 15. Thereafter, an exhaust gas j (high- purity hydrogen) from the fuel cell 15 is used a hydrogen for hydrogenate desulfurization in the hydrogenate desulfurizer 11.