NOVELTY - A fuel gas (P) containing sulfur component is supplied to normal-temperature desulfurizing agent (1a), and the desulfurizing agent is heated when dew point of fuel gas is more than a fixed temperature. Thus, sulfur component contained in fuel gas is desulfurized.    USE - Method for desulfurizing fuel gas containing sulfur component and producing reformed gas used as fuel for fuel cell electric power generation system (claimed).    ADVANTAGE - The fuel gas is efficiently desulfurized. The energy efficiency of fuel cell electric power generation system is improved. The desulfurizing agent is quickly heated. The state of modifier and fuel cell is reliably maintained for long period of time, and electric power is stably produced.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) desulfurizing apparatus (D), which has a desulfurization portion filled with the desulfurizing agent, a portion for introducing fuel gas into desulfurizing portion, a heating portion for heating desulfurizing portion at fixed temperature, a dew point sensor (Se1) for detecting dew point of fuel gas in introducing portion, and a control portion (32) for changing fixed temperature of heating portion based on detection output of dew point sensor; and    (2) fuel cell electric power generation system (S), which has the desulfurizing apparatus for removing sulfur compound from the fuel gas, and having container (C) filled with desulfurizing agent, a modifier (3) for generating reformed gas (R) containing hydrogen, by modifying desulfurized fuel gas, fuel cell (6) for generating electric power using reformed gas as fuel, and a heating unit (21) for heating the desulfurizing agent in container at 50-80 degrees C when dew point of fuel gas is 0 degrees C or more. The desulfurizing agent is copper-manganese oxide-type desulfurizing agent.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic view of fuel cell electric power generation system. (Drawing includes non-English language text)    Normal-temperature desulfurizing agent (1a)    Modifier (3)    Fuel cell (6)    Heating unit (21)    Control portion (32)    Container (C)    Desulfurizing apparatus (D)    Fuel gas (P)    Reformed gas (R)    Fuel cell electric power generation system (S)    Dew point sensor (Se1)