The invention provides an electromagnetic fuel oil supply device. A pump shell and an electromagnetic coil are mounted in a buoyancy shell of the electromagnetic fuel oil supply device. The electromagnetic coil is arranged outside the pump shell. The lower end of the pump shell is fixed in the buoyancy shell. An oil outflow valve is fixed in a center hole of the pump shell. 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 inflow channel of an oil inflow cavity and an oil inflow channel of an extrusion cavity are sealed through sealing cones or sealing balls. An oil distributing and limiting plate is fixed in a limiting hole in the upper end of the iron core piston. The sealing cones or the sealing balls are mounted in inner cone holes of the iron core piston. The electromagnetic fuel oil supply device is compact in structure and strong in power, can float on the fuel oil surface when pumping oil and can ascend or descend automatically along with ascent or descent of the fuel oil surface, and water and impurities at the bottom of a fuel oil tank cannot enter an oil pump.