An electric power generation system is mounted on a vehicle having a secondary battery, an electric load, and an internal combustion engine as a driving source consuming gasoline in a mixed fuel which mainly consists of the gasoline and ethanol. The electric power generation system has a fuel cell for generating electric power by electric chemical reaction and a fuel storage unit having an ethanol selection permeable membrane for separating the ethanol from the mixed fuel involving the ethanol and gasoline. On satisfying a given condition, the fuel cell receives the ethanol from the permeable membrane and initiates the generation of electric power, and supplies the generated electric power to at least one of the secondary battery and the electric load.