There is provided a phosphite composition comprising 100 parts by weight of a phosphite represented by the formula (1) and 0.5 to 8 parts by weight of an aliphatic hydrocarbon lubricant having a softening point or a melting point of not higher than 115.degree. C., wherein the content of the phosphite (1) in said composition is 30 to 99.5% by weight. ##STR00001##