Fuel-cell cars are expected to be an ultimate solution for accommodating clean environments with convenient personal transport system. In order to make fuel-cell cars more compact and more accessible, we need to solve the problem how to store hydrogen in a limited space on board. At present, a high-pressure gas cylinder is used for such purpose. If such cylinders are replaced by an advanced hydrogen storage system based on solid state hydrogen storage materials, we will get more space in fuel-cell cars and shorter time for refill hydrogen in a hydrogen gas-station. For such purpose, we propose the muSR experiment on hydrogen storage materials, LiAlH4 and NaAlH4, to know the hint how to improve their hydrogen desorption temperature. This is because muSR provides microscopic information on solids through the change in the internal nuclear magnetism.