NOVELTY - A desulfurizing apparatus (3) comprises desulfurizer (7) which accommodates desulfurization catalyst (7a) which removes sulfur content from raw fuel for supplying modifier which produces reformed gas, heating unit to heat desulfurization catalyst, raw fuel introduction unit to introduce raw fuel in desulfurizer, raw fuel drive unit to lead-out raw fuel from inside of desulfurizer, temperature measuring unit which measures temperature of desulfurization catalyst, and pressure measuring unit to measure pressure of raw fuel in desulfurizer.    USE - A desulfurizing apparatus used for fuel cell system (claimed).    ADVANTAGE - The decline in desulfurization efficiency is suppressed.    DETAILED DESCRIPTION - A desulfurizing apparatus (3) comprises desulfurizer (7) which accommodates desulfurization catalyst (7a) which removes sulfur content from raw fuel for supplying modifier which produces reformed gas, heating unit to heat desulfurization catalyst, raw fuel introduction unit to introduce raw fuel in desulfurizer, raw fuel drive unit to lead-out raw fuel from inside of desulfurizer, temperature measuring unit which measures temperature of desulfurization catalyst, pressure measuring unit to measure pressure of raw fuel in desulfurizer, acquisition unit to acquire numerical value corresponding to deterioration degree of desulfurization catalyst, and control unit which controls heating unit, raw fuel introduction unit and raw fuel leading-out unit. The control unit controls heating unit, raw fuel introduction unit and raw fuel leading-out unit so that pressure measured by pressure measuring unit and/or temperature measured by temperature measuring unit may raise according to increase in numerical value acquired by acquisition unit. An INDEPENDENT CLAIM is included for a fuel cell system.    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of desulfurizing apparatus used for fuel cell system. (Drawing includes non-English language text).    Desulfurizing apparatus (3)    Desulfurizer (7)    Desulfurization catalyst (7a)    Heater (8)    Inlet valve (9)