PURPOSE: To obtain a reformed oil which is well combustible or has a low pollution level, by introducing fuel oil and a heterogenous phase soln. into a magnetic field to separate oil and the soln. from each other by a rotor, to finely divide water and to bring oil into an excited state.

CONSTITUTION: Heavy oil C from a fuel oil-introducing pipe 7 and water from a heterogenous phase soln. introducing pipe 8 are introduced and rotated by a rotor 3. They are passed through holes of porous plates 4A, 4B or a space between the porous plate 4 and a casing 2 and transferred to a discharge side. Cavitation is caused in the neighborhood of the surfaces of the porous plates 4A, 4B, and water in the heavy oil is dipsersed and finely divided by impact force. The molecular bonds of combustible material-contg. compsn. in the oil are brought into an excited state which is easily dissociated, by high pressure and high temp. E.M.F. is produced in the oil and water by high-speed rotation so that the excited state is increased. Eddy current is generated by the rotor made of iron and hence, heat is generated. The temp. of the oil is elevated by this heat together with heat generated by cavitation, whereby the viscosity of the oil is lowered. The reformed oil is discharged through a discharge pipe 9 and fed to a boiler, an oven, etc.