A flow battery according to one aspect of the present disclosure includes: a first liquid containing dissolved therein a charge mediator and a discharge mediator; a first electrode immersed in the first liquid; and a first active material immersed in the first liquid. The equilibrium potential of the charge mediator is lower than the equilibrium potential of the first active material, and the equilibrium potential of the discharge mediator is higher than the equilibrium potential of the first active material.