To improve the efficiency of combustion in an internal combustion engine or a cumbustion apparatus and reduce nitrogen compound in exhaust gas.

This device comprises a bobbin body 12 having therein a fuel passage 16 where fluid fuel such as gasoline or combustible gas passes; a coil 14 formed of a specified number of turns around the outer circumference of the body 12; and a multi-surface body 18 made of magnetic metal being sealed in the passage 16 and allowing the fluid fuel to contactwise pass. By generating magnetic field through application of required voltage to the coil 14, and thereby magnetizing the multi-surface body 18 in the passage 16 for bringing the fluid fuel in the passage 16 into contact with the body 18 and making the same flow, the fluid fuel is reformed. An amorphous alloy may be used for the multi- surface body instead of the magnetic metal.