A method for purifying solid borazane (NH3BH3 (s)) includes a) bringing solid borazane (NH3BH3 (s)) containing impurities into contact with a stream of gaseous ammonia (NH3 (g)) to obtain, by selective liquefaction of the borazane, a liquid phase containing liquefied borazane and ammonia and a solid phase constituted of at least a part of the impurities, b) separating the liquid and solid phases for recovery of the liquid phase, on the one hand, and of the solid phase, on the other hand; c) removing the ammonia from the recovered liquid phase, this removal causing precipitation of the purified borazane (NH3BH3 (s′)); and d) recovering the purified precipitated borazane (NH3BH3 (s′)).