NOVELTY - The apparatus (1) has a container (2a) containing liquid fuel (F) and attached to a device. A joint (6) connects the container and the device, where the joint includes a double tube structure with cylindrical and coaxial outer and inner tubes. One of the outer and inner tubes form a flow path through which the fuel flows into the device by gravity and the other tubes form a flow path through which a replacement fluid e.g. air, flows into the container to replace the liquid fuel. The outer tubes form the path for the liquid fuel while the inner tube forms the path for the replacement fluid.    USE - Fuel supply apparatus for supplying a highly inflammable liquid fuel to portable and cordless medium-size electronic devices e.g. notebook personal computers and wireless speakers, and large-size electronic devices e.g. home use power generators for construction work, electric scooters and mobility scooters for elderly persons. Uses include but are not limited to methanol, polyethylene (PE), polypropylene (PP), polyether ether ketone (PEEK), polyphenylene sulfide (PPS) and polyethylene terephthalate (PET) fuel.    ADVANTAGE - The apparatus avoids pressing a fuel cartridge with the hand of a user, thus providing convenience for users and supplying the fluids continuously by gravity in an effective manner. The apparatus allows continuous operation of devices with fuel cells, which consume relatively large amounts of fuel for a long time. The apparatus allows valve mechanisms of a connector of the device to be opened first, and then valve mechanisms of the connector for the fuel cartridge are opened, thus preventing leakage of the fuel when the cartridge is attached and detached from the device. The apparatus stops the supply of the fuel automatically when the level of the liquid fuel in a built-in tank of the device rises to a predetermined position, and resumes the supply of the fuel automatically when the level of the liquid fuel lowers due to consumption of the fuel, thus supplying the fuel continuously without pressing the fuel cartridge with the hand, and hence improving convenience for users. The apparatus reduces the size of a joint and the fuel cartridge, thus reducing size of the devices in an easier manner.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for an electronic device comprising a fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a fuel supply apparatus.    Liquid fuel (F)    Fuel supply apparatus (1)    Container (2a)    Joint (6)    Conduit (14g)    Gas-liquid separating film (14i)