NOVELTY - A desulfurization system (20) consists of a dehumidifier (21), a desulfurizer (22), a regenerator (40), and bypass unit (24). The dehumidifier is provided with an adsorbent which adsorbs moisture content of raw fuel gas. The regenerator regenerates the dehumidifier by supplying a resurgent gas with steam partial pressure lower than that of raw fuel gas supplied to the humidifier to the dehumidifier. Bypass unit (24) bypasses the resurgent gas exhausted from the dehumidifier to the desulfurizer resurgent gas is supplied to the dehumidifier.    USE - Desulfurization system is used in fuel cell systems e.g. of solid polymer type, solid oxide type, and molten carbonate type.    ADVANTAGE - The desulfurization system suppresses malfunction of desulfurizer.    DETAILED DESCRIPTION - A desulfurization system consists of a dehumidifier, a desulfurizer, a regenerator, and bypass unit (24). The dehumidifier is provided with an adsorbent which adsorbs moisture content of raw fuel gas obtained by reforming hydrogen-containing gas. The desulfurizer desulfurizes the dehumidified raw fuel gas. The regenerator regenerates the dehumidifier by supplying a dehumidifier resurgent gas with steam partial pressure lower than that of raw fuel gas supplied to the humidifier, and/or high temperature to the dehumidifier. Bypass unit (24) bypasses the dehumidifier resurgent gas exhausted from the dehumidifier to the desulfurizer when the regenerator supplies resurgent gas to the dehumidifier. An INDEPENDENT CLAIM is included for control method of desulfurization system, which involves regenerating the dehumidifier and bypassing the resurgent gas.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of a fuel cell system consisting of the desulfurization system. (Drawing includes non-English language text)    Desulfurization system (20)    Dehumidifier (21)    Desulfurizer (22)    Bypass units and flow-path form selection unit (23,24)    Regenerator (40)    Fuel cell (70)    Cathode (71)