According to the present invention, there is provided a fuel supply system employing an ultrasonic vibratory member of a hollow cylindrically shaped body, comprising a fuel tank for storing fuel therein; a pressurizing and regulating means for pressurizing the fuel supplied from the fuel tank to a predetermined pressure level and regulating the flow rate of the fuel; an ultrasonic wave generating means comprising an ultrasonic wave transducer connected to an ultrasonic wave oscillator for transforming an electric oscillation into mechanical vibrations, a mechanical vibration amplifying portion which is integrally secured to the ultrasonic wave transducer, and an ultrasonic vibratory member of a hollow cylindrically shaped body, having a predetermined length and diameter, which is integrally secured to an output end of the mechanical vibration amplifying portion, with the axis of the member being directed perpendicularly to the axis of the mechanical vibration amplifying portion; and liquid film forming means, connected to the pressurizing and regulating means, having an exit provided at the position adjacent to the ultrasonic vibratory member of the hollow cylindrically shaped body, forming a thin film of supplied fuel and supplying the fuel film from the exit to the ultrasonic vibratory member of the hollow cylindrically shaped body.