We show a drastically improved gas–solid reaction between NH3 and LiH by mechanical treatment for LiH, generating a hydrogen gas even at room temperature. The results of x-ray photoelectron spectroscopy showed that the mechanical pretreatment was effective in reducing a hydroxide phase from the surface of LiH. It was also possible to successfully recycle back LiNH2, which is the byproduct of this hydrogen desorption reaction, to LiH under 0.5-MPa H2 flow at 573 K. Thus, the LiH–NH3 system provides a recyclable H2 storage system to generate H2 at room temperature with 8.1 mass% and 4.5 kg/100 L hydrogen capacity.