The invention discloses a magnetizing fuel oil saving device. The magnetizing fuel oil saving device comprises an outer shell (1), an oil inlet pipe (2), an oil outlet pipe (3), inner shells (4) and magnets (5). The magnetizing oil saving device is characterized in that the inner shells (4) are arranged in the outer shell (1), the magnets (5) are arranged in the inner shells (4), and the oil inlet pipe (2) and the oil outlet pipe (3) are located at the two ends of the outer shell (1) respectively; the magnets (5) comprise two pairs of main magnets (51) and deputy magnets (52), a spacing piece (6) is arranged between each pair of the main magnet (51) and deputy magnet (52), the two sides of the magnets (5) are provided with ceramic wafers (7), the inner shells (4) are fixed in the outer shell (1), the main magnets (51) and the deputy magnets (52) form magnetic bodies, the ceramic wafers (7) can reduce magnetic field loss, and the spacing pieces (6) can improve oil saving effect. The magnetizing oil saving device magnetizes fuel oil, the atomization effect is improved obviously, the fuel oil is adequately combusted, the combustion efficiency of the fuel oil is improved, and the fuel oil is saved.