To provide a method for producing highly purified amine boranes having excellent crystallinity by using economical raw materials and through a simple treatment.

This method comprises a process for reaction between an amine salt and sodium borohydride in dimethoxyethane, a process for decomposing residual or unreacted amine salt with an aqueous solution of sodium hydroxide or potassium hydroxide, a process for separating an upper layer containing a large amount of amine borane from a lower layer of an aqueous solution with a small amount of amine borane dissolved therein, a process for recovering the amine borane through treatment of the lower layer of the aqueous solution with dichloromethane or benzene having excellent solvency for amine borane and a process for mixing residual or unreacted dichloromethane with the upper layer followed by distillation to remove it and purify the amine borane.