Microstructures and hydrogen storage properties of Mg-Al super laminate composite alloys were investigated. The laminated sample was made by alternately stacking Mg films and Al films. The laminate was subjected to repetition of stacking and cold-rolling under an ambient condition (super lamination technique), combined with final heat treatment under an argon gas atmosphere. The number of films and thickness was nearly 15000 layers and about 50μm, respectivery. Their microstructures and hydrogen storage properties were studied by scanning electron microscopy, X-ray diffractometry and volumetric method by use of a Sieverts-type apparatus. In heat treatment process at 673K, Mg17Al12 intermetallic compound was formed by interdiffusion. This compound absorbed and desorbed hydrogen reversibly through the disproportionation and recombination react at 673K.