Recently, high energy density battery attracts public attention with the application to power source of electric vehicle and electric energy storage system in solar and wind generation. Magnesium electrode has large theoretical capacity as much as 3839 mAh cm-1. Besides, magnesium compounds are abundant in the earth's crust and most of them are nontoxic. Therefore, rechargeable magnesium battery, whose negative electrode reaction is magnesium deposition / dissolution, is one of the most expected candidates.However, rechargeable magnesium deposition and dissolution is not achieved in most electrolytes. Magnesium has extensively high reactivity, leading the formation of surface films in the electrolytes. These films cannot conduct magnesium ion and inhibit magnesium deposition and dissolution reactions. So far, reversible magnesium deposition and dissolution can be achieved only in RMgX (R = alkyl or aryl, X = halogen), Mg(BR4)2 or Mg(AlCl2RR')2 / ether solutions [1,2,3]. In these solutions, magnesium is thought not to be covered with surface films. However, since these solutions have limitation for the battery electrolyte, due to their thermal and chemical instability, studies for more proper electrolytes are needed.In this work, we focused on the electrolyte consisting of magnesium bromide and 2-methyltetrahydrofuran (2-MeTHF), which were composed of Grignard reagents. The electrochemical behavior of platinum electrode in the solution and the analysis of deposits were studied in detail.