Provided is a floating fuel oil supplying device. A pump shell and an electromagnetic coil are installed in a buoyancy shell of the floating fuel oil supplying device; the electromagnetic coil is arranged outside the pump shell which is fixed in the buoyancy shell; an oil outlet valve is fixed in a center hole; an iron core spring and an iron core piston are arranged in the pump shell; the iron core spring is pressed on the iron core piston; an oil inlet channel of an oil inlet cavity is sealed by a sealing cone or a sealing ball, and an oil inlet channel of an extrusion cavity is sealed by a passed oil sealing plate; an oil dividing limiting plate is fixed in a limiting hole in the upper end of the iron core piston; the sealing cone or the sealing ball is installed in an inner conical ball of the iron core piston. The floating fuel oil supplying device is compact in structure, strong in power and capable of floating on a fuel oil face during oil pumping and automatically ascending or descending along with ascending or descending of the fuel oil face, and water and impurities at the bottom of a fuel oil tank cannot enter an oil pump.