NOVELTY - The desulfurizer (200) has an outer container (201) that is provided with outer container inlet (203) and outer container outlet (204). An inner container (208) has an inner container inlet and outlet (211, 212) that are connected to the inlet and outlet of outer container respectively by sealing portions. The inner container has a desulfurizing portion (221) that is filled with the desulfurizing agent (209) so as to remove odorant in fossil raw materials. A contact portion is formed in the inlet and outlet of outer container.    USE - Desulfurizer for hydrogen generator used in fuel cell electric power generation system (both claimed).    ADVANTAGE - The deterioration of the desulfurizing agent can be suppressed effectively at the time of replacement of the desulfurizing agent. The odorants such as sulfur components can be removed from the fossil raw materials reliably.    DETAILED DESCRIPTION - Several elastic portions are formed in a partition portion of the inner container. The inlet and outlet of the inner container is opened by the elastic portions, when the inner container is arranged inside the outer container. The inlet and outlet of the outer container is closed by the elastic force generated by the elastic portions, when the inner container is removed from the outer container. Several through-holes are formed in the wall portions of the inner and outer containers. The through-holes are closed by the sealing portions. INDEPENDENT CLAIMS are also included for the following:    (1) hydrogen generator has a modification unit that performs modification reaction of raw material so as to generate the hydrogen-containing gas;    (2) fuel cell electric power generation system has a fuel cell that utilizes the hydrogen-containing-gas supplied from the hydrogen generator; and    (3) desulfurization-agent cartridge.    DESCRIPTION OF DRAWING(S) - The drawing shows a sectional view of the desulfurizer.    Desulfurizer (200)    Outer container (201)    Outer container inlet (203)    Outer container outlet (204)    Inner container (208)    Desulfurizing agent (209)    Inner container inlet (211)    Inner container outlet (212)    Desulfurizing portion (221)