Rechargeable magnesium battery using magnesium metal for anode is attracting candidate for post-lithium ion batteries, because magnesium has a larger volumetric capacity (about 3830mAhcm-3) than that of lithium (about 2060mAhcm-3), and its resources are abundant in the earth's crust. It is required for the operation of rechargeable magnesium battery that a magnesium anode is not passivated and the diffusion of magnesium ion in the cathode material is fast. We indroduce the Maglution® series that is electrolytic solution for rechargeable magnesium containing a boron-based magnesium salt developed in our company.