Decomposition of an aqueous electrolyte solution when an aqueous lithium ion secondary battery is charged and discharged is suppressed, and the operating voltage of the battery is improved. The aqueous lithium ion secondary battery includes an anode, a cathode, and an aqueous electrolyte solution, the anode including a composite of an anode active material and polytetrafluoroethylene, wherein peaks of the polytetrafluoroethylene at around 1150 cm−1 and at around 1210 cm−1 are observed in FT-IR measurement of the composite, but a peak of the polytetrafluoroethylene at around 729 cm−1 is not observed in Raman spectroscopy measurement of the composite.