Electrolysis of an aqueous electrolyte solution on a surface of an anode is suppressed when an aqueous lithium ion secondary battery is charged/discharged. In an aqueous electrolyte solution that is used for an aqueous lithium ion secondary battery, at least one metal cation selected from an aluminum ion, a titanium ion, a manganese ion, a zinc ion, a gallium ion, a yttrium ion, a zirconium ion, an indium ion, a lanthanum ion, a cerium ion, a neodymium ion, and a hafnium ion is contained so that its content is more than 0 mol and no more than 0.01 mol per kilogram of the aqueous electrolyte solution, in addition to a lithium ion and at least one imide based anion.