This invention provides a technique which even in an environment without light or with little light irradiation, achieves potent reduction, reduces, by a photocatalytic effect, the oxidation and deterioration of oil when used in edible oil used for fried foods, improves the state of fried foods, attains excellent frying even at lower temperature, exhibits the effect for a long time, has an ability to recycle waste oil as biofuel, and is excellent in food safety. Although a photocatalyst itself is extremely effective outdoors with much ultraviolet light or when an ultraviolet light emitting light is used, the photocatalyst cannot exhibit its functions indoors, in oil in a fryer, or in water. This invention provides a durable reduced photocatalyst which can exhibit significant photocatalytic functions in oil in a fryer, in water, or in the dark, to exert its long-lasting effect. The object is achieved by a functional oil oxidation-inhibiting 4-layered spherical ceramics, wherein a 4-layered spherical composition consisting of 4 mixtures that are a mixture consisting of powdery soil clay and powdery anion active core ceramics solidified and formed into a first layer core, a mixture consisting of powdery soil clay and powdery titanium oxide solidified and formed into a second layer core, a ceramic mixture consisting of powdery soil clay and powdery activated charcoal solidified and formed into a layer, and a mixture consisting of platinum powder and titanium oxide adhered on the surface of the ceramic mixture, is used in dipping in edible oil.