NOVELTY - The hydrogen generating apparatus (50) has modifier (1), transformer (6), water supply device (3A), raw material supply unit (2A), and control unit (12). The modifier reforms the raw material and produces reformed gas. The control unit counts number of times of start and/or stops of the apparatus, and elevates temperature or steam/carbon (S/C) ratio of reformed gas flowing through modifier based on counted number.    USE - For generating hydrogen used for fuel cell system (claimed).    ADVANTAGE - The hydrogen production apparatus simply enables to produce hydrogen with high reliability. The hydrogen production apparatus enables to supply reformed gas with low content of carbon monoxide for long period of time.    DETAILED DESCRIPTION - The hydrogen generating apparatus (50) has a modifier (1), a transformer (6), a water supply device (3A) for supplying water to modifier, a raw material supply unit (2A) for supplying raw material to modifier, and a control unit (12). The modifier reforms the raw material by water vapor modification reaction and produces reformed gas containing carbon monoxide, water and hydrogen. The transformer performs transformation reaction of carbon monoxide and water vapor contained in reformed gas. The control unit counts number of times of start and/or stops of the apparatus, and elevates temperature or S/C ratio of reformed gas flowing through modifier based on counted number.    INDEPENDENT CLAIMS are also included for the following:    (1) fuel cell system, which has a fuel cell and hydrogen production apparatus for supplying reformed gas to fuel cell. The fuel cell system controls feed rate of reformed gas based on electrical power generation output of fuel cell. The control unit of hydrogen production apparatus counts start and/or stop of fuel cell; and    (2) operation of hydrogen production apparatus, which involves counting start and/or stop of hydrogen production apparatus, and raising temperature or S/C ratio of reformed gas passing through transformer based on counted number.    DESCRIPTION OF DRAWING(S) - The figure shows the block diagram of hydrogen production apparatus. (Drawing includes non-English language text).    modifier (1)    raw material supply unit (2A)    water supplying device (3A)    transformer (6)    control unit (12)    hydrogen production apparatus (50)