In, for example, a direct methanol type fuelcell, fuel is allowed to be injected little by little when the fuel is injected and supplied from the outside to a fuel receiving part reduced in the amount of remaining fuel on the fuelcell body side and an electromotive part can be prevented from being damaged by keeping the pressure in the fuel receiving part at a fixed level or less when the fuel is injected. Specifically, when a fuel CL filled in a refuelling container C is injected into a fuel receiving part T in several lots, a fuel injecting operation is repeated in which the volume of the refuelling container C is shrunk and reduced to supply the fuel into the fuel receiving part T in a proper amount and then the original volume of the refuelling container is restored to thereby absorb the atmospheric gas in the fuel receiving part T, which makes it possible to inject fuel continuously without any hindrance to the injection of the fuel.