Industrial oil composition

An industrial oil composition, comprising;

• a mineral or a synthetic oil as a base oil, and
• a neutral phosphite ester derivative represented by the following formula (B) and a 2,6-di-t-butylphenol derivative represented by the following formula (C) as antioxidants:
• in the formula (B), Rb21 to Rb24 each independently represent an aliphatic hydrocarbon group of 10 to 16 carbon atoms, Rb25 to Rb28 each independently represent a straight-chain or branched alkyl group of 1 to 6 carbon atoms, Rb291 and Rb292 each independently represent a hydrogen atom or a straight-chain or branched alkyl group of 1 to 5 carbon atoms, and a total number of carbon atoms of Rb291 and Rb292 is 1 to 5,
• in the formula (C), Rc1 represents a straight-chain or branched alkyl group of 1 to 12 carbon atoms,
• wherein the synthetic oil comprises a phosphate ester derivative, tris(isopropylphenyl) phosphate, and triphenyl phosphate,
• the phosphate ester derivative has a repeating unit represented by the following formula (A1), a structure represented by the following formula (A2) at one end, and a structure represented by the following formula (A3) at another end, and a kinematic viscosity at 40° C. is in a range of not less than 100 cSt and not more than 200 cSt:
• and
• triphenyl phosphate is present in an amount of 1.5% to 92.15% by mass of the synthetic oil.