NOVELTY - A fuel cell device has: tank section (76) for accommodating hydrogen storage alloys (80); power generating section for generating electric power using hydrogen desorbed from tank section; pressure detecting unit for detecting pressure of the hydrogen supplied to the power generating section; and output section for outputting pressure variations.    USE - Used as fuel cell device.    ADVANTAGE - The invention is capable of outputting signal representing residual hydrogen amount.    DETAILED DESCRIPTION - The fuel cell device capable of outputting signal representing residual hydrogen amount comprises tank section for accommodating hydrogen storage alloys having mutually different hydrogen desorbing characteristics; power generating section for generating electric power using hydrogen desorbed from the tank section; pressure detecting unit for detecting pressure of the hydrogen supplied to the power generating section; and output section for outputting pressure variations caused on the basis of hydrogen desorbing characteristics of the hydrogen storage alloys which are detected by the pressure detecting unit.    INDEPENDENT CLAIMS are also included for:    (a) a method for outputting signal representing residual fuel cell capacity in a system including a tank section for accommodating hydrogen storage alloys having mutually different hydrogen desorbing characteristics and a power generating section for generating electric power using hydrogen desorbed from the tank section, comprising: detecting a pressure of the hydrogen supplied to the power generating section; and outputting pressure variations caused on the basis of hydrogen desorbing characteristics of the hydrogen storage alloys;    (b) an electronic device capable of detecting residual capacity of fuel cell device, comprising: tank section; power generating section; pressure detecting unit; residual amount detecting unit for detecting residual hydrogen amount using pressure variations caused on the basis of hydrogen desorbing characteristics of the hydrogen storage alloys; and control unit which operates with the electric power supplied from the power generating section; and    (c) a method for detecting residual fuel cell capacity of the electronic device, comprising: detecting pressure of the hydrogen supplied to the power generating section; detecting residual hydrogen amount using pressure variations caused on the basis of hydrogen desorbing characteristics of the hydrogen storage alloys; and causing a control section to operate with the electric power supplied from the power generating section.    DESCRIPTION OF DRAWING(S) - The figure is a view showing the tank section.    Fuel tank (76)    Hydrogen storage alloy (80)    Pressure sensor (81)    Output circuit (82)    Temperature sensor (83)