Abstract: To provide a deterioration control oil filter capable of increasing an effect for purifying pollutants, floating matters, or the like in a lubricating oil or a hydraulic oil as well as increasing an effect for suppressing the oxidation of the lubricating oil or the hydraulic oil. A long filtration functioning distance using mineral particles 30 can be secured, since an oil inlet pipe 24 for discharging the lubricating oil or the hydraulic oil into the casing 29 is connected to a bottom center of the casing which is isolated from the atmosphere, an oil outlet pipe 25 is connected to a bottom of the casing 29, and the mineral particles 30 are provided in the casing 29 interspacially at an upper portion of the casing, thereby allowing the lubricating oil to circulate in the casing in an up-and-down direction.