NOVELTY - A hydrogen generator (2) is provided with material provisioning portion (4), water supplying unit (5), modified-catalyst layer, heating unit and several temperature detecting unit. A modified-catalyst layer (19) is interposed through an inner cylinder (14) and outer cylinder (13). The raw material and water are reacted, to generate reformed gas. The temperature detectors detect the temperature of reformed gas on center axis of inner or outer cylinder. The temperature detector uses high value detection temperature for controlling temperature of modification portion (8).    USE - Hydrogen generator is used for fuel cell power generating device (claimed).    ADVANTAGE - The hydrogen generator is highly reliable, and has improved durability. The high temperature deterioration of modified catalyst due to extended working conditions is prevented. The electric power load of fuel cell power generating device comprising hydrogen generator is generable.    DETAILED DESCRIPTION - A hydrogen generator is provided with a material provisioning portion which supplies raw material, a water supplying unit, a modified-catalyst layer, a heating unit and several temperature detecting unit. A modified-catalyst layer is interposed through an inner cylinder and outer cylinder. The raw material which is supplied from material provisioning portion, and water supplied from water-supplying portion are reacted, and reformed gas is generated by heating modified-catalyst layer. The temperature detectors detect the temperature of reformed gas on periphery-centering portion on center axis of inner cylinder or outer cylinder. The temperature detector uses high value detection temperature for controlling temperature of modification portion.    DESCRIPTION OF DRAWING(S) - The drawing shows a structural view of hydrogen generator.    Fuel cell (1)    Hydrogen generator (2)    Material provisioning portion (4)    Water supplying portion (5)    Modification portion (8)    Outer cylinder (13)    Inner cylinder (14)    Modified-catalyst layer (19)