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

There are disclosed a hydroboration method of an organic compound having a carbon-carbon unsaturated bond wherein a composition comprising borane and tetrahydropyran is employed, and a method for producing a reaction product of hydroboration, comprising adding water subsequent to the hydroboration reaction and extracting a compound resulting from the reaction into the tetrahydropyran layer.