NOVELTY - The hydrogen generating apparatus useful in a fuel cell power generation system, comprises an electrolyzer filled with an aqueous electrolyte solution, a first electrode (220) and a second electrode (230) accommodated in the electrolyzer and submerged in the aqueous electrolyte solution, a switch (530) located between the electrodes, a flow rate meter (510) measuring an amount of hydrogen generation in the second electrode, and a switch controller (520) receiving a set value and comparing the amount of hydrogen generation measured by the flow rate meter with the set value.    USE - The hydrogen generating apparatus is useful in fuel cell power generation system (claimed).    ADVANTAGE - The hydrogen generating apparatus is capable of controlling the amount of hydrogen generation supplied to a fuel cell, is economical and eco-friendly, and can prevent waste or risk of leaking surplus hydrogen in the air simply by turning on the switch and reduce the noise and power consumption without using a gas pump or a liquid pump.    DETAILED DESCRIPTION - The hydrogen generating apparatus useful in a fuel cell power generation system, comprises an electrolyzer filled with an aqueous electrolyte solution, a first electrode (220) and a second electrode (230) accommodated in the electrolyzer and submerged in the aqueous electrolyte solution, a switch (530) located between the electrodes, a flow rate meter (510) measuring an amount of hydrogen generation in the second electrode, and a switch controller (520) receiving a set value, comparing the amount of hydrogen generation measured by the flow rate meter with the set value and controlling an on/off status of the switch. The first electrode generates electrons, and the second electrode receives the electrons to generate hydrogen. The hydrogen generating apparatus is coupled to a fuel cell and supplies hydrogen. The switch controller is inputted with the set value directly from a user through an input device and with the set value in accordance with an amount of hydrogen generation that is required by the fuel cell. A metal forming the first electrode has a higher ionization tendency than a metal forming the second electrode. The flow rate meter measures the amount of hydrogen generation in units of flow rate. The switch controller generates and outputs a switch control signal turning the switch on and off, and determines an on/off ratio of the switch within one cycle by varying a duty ratio of the switch control signal. The set value comprises an upper limit and a lower limit. The switch controller controls a fluctuation in the amount of hydrogen generation by varying an on/off frequency of the switch control signal, compares the set value with the measured amount of hydrogen generation, increases the duty ratio if the amount of hydrogen generation is smaller than the lower limit, reduces the duty ratio if the amount of hydrogen generation is greater than the upper limit, and maintains the duty ratio if the amount of hydrogen generation is between the lower limit and the upper limit. INDEPENDENT CLAIMS are included for:    (1) a fuel cell power generation system; and    (2) a method of controlling an amount of hydrogen generation in a hydrogen generating apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows a block diagram of a control unit of a hydrogen generating apparatus.    First electrode (220)    Second electrode (230)    Flow rate meter (510)    Switch controller (520)    Switch. (530)