[Object] It is aimed at applying an electromagnetic wave treatment technique to an edible oil or industrial oil, thereby establishing a method for preventing deterioration of the edible oil or industrial oil, and an apparatus therefor.[Solving means] A fluororesin-coated electric wire cable (5) is wound around a ring-shaped groove defined by an outer periphery of a cylinder (11a) and two flange edges (11b, 11b) immersed in an edible oil (7) in a tank (6), thereby forming each oscillating unit (16) having a coil part (2) and the oscillating units are connected to an electromagnetic wave generator (10) through a relay unit (13). Electromagnetic waves are irradiated from the coil parts (2) based on an alternating current having a single frequency, an alternating current having a plurality of single frequencies different from one another, or an alternating current having a timewise varying frequency, the alternating currents each being within a frequency band of 4kHz to 25kHz, and a treatment based on a far-infrared heater or far-infrared ceramic is used combinedly therewith, to prevent deterioration of an edible oil or industrial oil.
