PURPOSE: To activate a liq. or gaseous fuel to improve its combustion efficiency and decrease the amts. of harmful org. substances generated during combustion by exposing the fuel to magnetic lines of force and far-infrared rays.

CONSTITUTION: A fuel-activating apparatus A is obtd. by installing, in a nonmagnetic stainless-steel tube 6, tubular or annular ceramic bodies 3 which radiate farinfrared rays and tubular or annular magnets 1 which provide magnetic lines of force and are fixed in parallel or arranged closely to each other at both ends of the ceramic bodies 3 so that one magnet 1 and the other magnet 1 form a complicated magnetic field comprising an attracting magnetic field 4 and a repulsing magnetic field 5. A liq. or gaseous fuel is supplied through a delivery pipe 7 to through-holes 2, 2' of the fuel combustion base and activated by characteristic actions of magnetic lines of force provided by the magnets 1 and infrared rays radiated from the ceramic bodies 3.