The present disclosure provides a flow battery including a lithium ion conducting film that has flexibility and that has durability against a nonaqueous electrolyte having high reducing power. A flow battery according to the present disclosure includes a first nonaqueous electrolyte, a first electrode, a second electrode, and a lithium ion conducting film. The first nonaqueous electrolyte contains lithium ions and further contains biphenyl, phenanthrene, stilbene, triphenylene, anthracene, acenaphthene, acenaphthylene, fluorene, fluoranthene, o-terphenyl, m-terphenyl, or p-terphenyl. The lithium ion conducting film contains: lithium ion conducting polymers to which a lithium salt of an acidic group is introduced and that include an aromatic ring; and polyvinylidene fluoride. The lithium ion conducting polymers and the polyvinylidene fluoride are mixed uniformly with each other in a composite.