NOVELTY - A hydrogen generating apparatus (1) comprises desulfurizer (2) which removes sulfur component from source gas, modifier (3) which produces hydrogen-containing gas by reforming reaction with source gas and modification water which are discharged from desulfurizer, material supply path (4) which supplies source gas to desulfurizer, discharge path (5) which discharges hydrogen-containing gas from modifier, water supply machine (6) which supplies modification water to modifier, and material supply device (7).    USE - A hydrogen generating apparatus for fuel cell system (claimed).    ADVANTAGE - Abnormal flow of hydrogen-containing gas flowing through recycle path can be detected.    DETAILED DESCRIPTION - A hydrogen generating apparatus (1) comprises desulfurizer (2) which removes sulfur component from source gas, modifier (3) which produces hydrogen-containing gas by reforming reaction with source gas and modification water which are discharged from desulfurizer, material supply path (4) which supplies source gas to desulfurizer, discharge path (5) which discharges hydrogen-containing gas from modifier, water supply machine (6) which supplies modification water to modifier, material supply device (7) of constant volume which is positioned on material supply path and supplies source gas of predetermined volumetric flow rate to modifier with respect to predetermined operating quantity, mass flowmeter measurement apparatus (8) which is positioned on material supply path and measures mass flow rate of source gas, recycle path (9) which supplies part of hydrogen-containing gas discharged from modifier to desulfurizer, and controller (10). When difference between volumetric flow rate of source gas computed by material supply device based on operating quantity of material supply device and mass flow rate of source gas measured by mass flowmeter measurement apparatus exceeds predetermined flow volume range, flow volume of hydrogen-containing gas which is discharged from modifier and flows into recycle path is judged to be abnormal. An INDEPENDENT CLAIM is included for fuel cell system provided with hydrogen generating apparatus (1) and fuel cell which generates power by reacting oxygen-containing gas and hydrogen-containing gas discharged from discharge path (5).    DESCRIPTION OF DRAWING(S) - The drawing shows a block diagram of the hydrogen generating apparatus.    Hydrogen generating apparatus (1)    Desulfurizer (2)    Modifier (3)    Material supply path (4)    Discharge path (5)    Water supply machine (6)    Material supply device (7)    Mass flowmeter measurement apparatus (8)    Recycle path (9)    Controller (10)