To solve problems such as maintaining the stability of borane, preventing odor, and decrease of reactivity, by selecting tetrahydropyran that makes borane readily usable in the reduction reaction of borane.

There are disclosed a reduction method of an organic compound wherein a composition comprising borane and tetrahydropyran is employed, and a method for producing a reduction product of the organic compound comprising adding water subsequent to the reduction of the organic compound and extracting a compound resulting from the reaction into the tetrahydropyran layer. The reduction method is applicable to a wide variety of organic compounds such as a carbonyl compound, an ester compound, a carboxylic acid compound, an amide compound, and a nitrile compound.