Hydrogen generator, a method operating the hydrogen generating apparatus, a method of operating a fuel cell system and a fuel cell system

Providing detectable hydrogen generator such as a transformer or the interior of the water excess or steam Excessive amount of selective oxidation device by a simple method. Hydrogen generator (120), a reformer for generating a reformed gas from a raw material and water vapor (100), a transformer for the shift reaction the supplied reformed gas from the reformer (100) and (103), selective oxidizer to reduce the carbon monoxide gas concentration in the reaction gas in the shift reaction to a predetermined concentration or less (105) the hydrogen generator including a (118), the transformer of the (103) and the selective oxidation unit (105) a temperature detector for detecting the temperature either (116, 117), configured to include a control unit (205), the. The control device (205), the temperature sensing portion Atsushi Nobori rate of the detected temperature detected is by (116, 117), if it is less than the predetermined threshold, the inside of the water or water vapor of the hydrogen generator (118) the amount is detected as excessive state.