The object is to provide a method for drying and storing activated aluminum fine particles which can be a hydrogen source for fuel cells for a long term without being deactivated. A thermal shock treatment as an activation of the aluminum fine particles, which repeats rapid heating and cooling, is performed to aluminum fine particles obtained by milling aluminum alloy; moisture contained in the activated aluminum fine particles is filtrated; said aluminum fine particles are pre-frozen; and the aluminum fine particles are freeze-dried and then stored in nitrogen atmosphere or vacuum-packed.