Micro/nano-structures and hydrogen storage properties of Mg/Cu super-laminates were investigated. Mg/Cu super-laminates showed reversible hydrogenation and dehydrogenation at 473 K. In order to clarify the process of hydrogenation and dehydrogenation at 473 K, we performed TEM observations of micro/nano-structures of the Mg/Cu super-laminates and Mg2Cu powder prepared by conventional casting method. TEM observations revealed that the as-rolled Mg/Cu super-laminates had laminated structures in size of sub-micrometer thickness composed of Mg and Cu layers with dense lattice defects. The super-laminates after initial activation kept laminated structures and had uniformly distributed pores with a sub-micrometer diameter. On the other hand, the cast Mg2Cu powder after initial activation had pores only beneath the surface oxide layers. It is considered that these micro/nano-structures of Mg/Cu super-laminates lead to lower dehydrogenation temperature and better kinetics, which would contribute to achieve high-performance hydrogen storage materials.