NOVELTY - The desulfurizer (6) has communication ports (613,614) provided at side of internal peripheral surface (610) of storage unit (61) in opened state, so that flow of fuel gas through port is permitted. The sealants (92-94) are provided contacting internal peripheral surface of storage unit. A ventilation hole is formed penetrating wall portions of container main structure corresponding to opening position of ports. The double-sealant (92,94) are provided for sealing both end positions of ports, while the intermediate position of ports is sealed by sealant (93).    USE - Desulfurizer for removing sulfur compound in fuel gas supplied to solid oxide fuel cell in fuel cell system (claimed).    ADVANTAGE - The replacement of desulfurizing agent in desulfurizer is performed efficiently, without stopping the operation of fuel cell, so that the removal of sulfur compound in fuel gas is performed reliably, and energy consumption of the fuel cell system is reduced efficiently.    DETAILED DESCRIPTION - A cylindrical cover portion (10) is attached integrally in desulfurizer before loading with desulfurizing agent cartridge (9) into the storage unit. The fuel gas is enclosed in the interior of container main structure in a state at which one end of container main structure and one sealant contacts with respect to internal peripheral surface of storage unit. An INDEPENDENT CLAIM is included for fuel cell system, which includes a battery main portion accommodated in the housing (2). A fuel gas supply path (31) supplies the fuel gas with respect to battery main portion. A buffer tank is provided at the downstream fuel gas supply path (32) of the desulfurizer.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross sectional view explaining the procedure of replacement operation of desulfurizing agent cartridge in desulfurizer.    Housing (2)    Desulfurizer (6)    Desulfurizing agent cartridge (9)    Cylindrical cover portion (10)    Fuel gas supply paths (31,32)    Storage unit (61)    Sealants (92-94)    Internal peripheral space of storage unit (610)    Communication ports (613,614)