NOVELTY - The fuel cell system (1) useful in an electronic device, comprises a power generation section (110) having an electrolytic solution between a fuel electrode and an oxygen electrode, a section supplying fuel to the fuel electrode and a control section (130) making the fuel supply section stop supplying the fuel thus performing electrolytic solution cleaning to remove a fuel contained in the electrolytic solution. The control section determines the timing of performing the electrolytic solution cleaning based on a generated current, a generated voltage and a generated electric power.    USE - The fuel cell system is useful in an electronic device (claimed) such as a mobile phone, a personal digital assistant and or a notebook personal computer and electric automobiles as a power source.    ADVANTAGE - The fuel cell system is capable of suppressing influence of fuel crossover and achieving long-time power generation without using a complicated separation mechanism, and has high energy density and high output density thus providing multifunction and high performance to the electronic device.    DETAILED DESCRIPTION - The fuel cell system (1) useful in an electronic device, comprises a power generation section (110) having an electrolytic solution between a fuel electrode and an oxygen electrode, a section supplying fuel to the fuel electrode and a control section (130) making the fuel supply section stop supplying the fuel thus performing electrolytic solution cleaning to remove a fuel contained in the electrolytic solution. The control section determines the timing of performing the electrolytic solution cleaning based on a generated current, a generated voltage and a generated electric power of the power generation section. A mechanism is used for measuring a concentration of the electrolytic solution. The control section detects an amount of the fuel contained in the electrolytic solution based on a measurement result of the mechanism, and determines the timing of performing the electrolytic solution cleaning based on a detected value. The control section makes the power generation section to stop functioning during a period of the electrolytic solution cleaning. A section (140) is arranged for circulating the electrolytic solution between the electrolytic solution supply section and the power generation section.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an electronic device including a fuel cell system.    Fuel cell system (1)    Power generation system (110)    Measurement section (120)    Control section (130)    Electrolytic solution supply section. (140)