An electrolytic solution containing a heteroelement-containing organic solvent at a mole ratio of 3-5 relative to a metal salt, the heteroelement-containing organic solvent containing a specific organic solvent having a relative permittivity of not greater than 10 and/or a dipole moment of not greater than 5D, the metal salt being a metal salt whose cation is an alkali metal, an alkaline earth metal, or aluminum and whose anion has a chemical structure represented by general formula (1) below: (R1X1)(R2SO2)N  general formula (1).