To obtain an additive which gives an excellent wear resistance and an excellent scoring resistance to a traction drive oil by blending a boron- containing phosphoric acid derivative having a specific absorbance in each of a phosphorus nuclear magnetic resonance spectroscopic measurement and a boron nuclear magnetic resonance spectroscopic measurement.

A boron-containing phosphoric acid derivative having an absorbance at 10 to -5 ppm in a phosphorus nuclear magnetic resonance spectroscopic measurement and absorbances both at 5 to -ppm and/or at -20 to -25 ppm is added to an additive for a traction drive oil. Although the composition and the structure of the boron-containing phosphoric acid derivative are not limited, a reaction product between a phosphorus compound such as a phosphoric ester, an acidic phosphoric ester, a phosphonic ester or the like, and a boron-containing compound such as boric acid, a boric ester, a boron- containing imide or the like, is preferably cited.