Niobium hydride powders could be formed by a mechanochemical reaction at room temperature and at 1 atm. Niobium metal powder was ball-milled with liquid decalin and liquid tetralin. With decalin, niobium metal continuously changed to niobium hydride. Otherwise with tetralin, niobium hydride separately precipitated from niobium metal. It is considered that this hydrogenation was caused by a fresh surface effect which was made by ball-milling.