A redox flow (RF) battery performs charge and discharge by supplying a positive electrode electrolyte and a negative electrode electrolyte to a battery cell. Each of the positive electrode electrolyte and the negative electrode electrolyte contains a vanadium (V) ion as active material. At least one of the positive electrode electrolyte and the negative electrode electrolyte further contains another metal ion, for example, a metal ion such as a manganese ion that exhibits a higher redox potential than a V ion or a metal ion such as a chromium ion that exhibits a lower redox potential than a V ion.