Disclosed is an ion conductive film containing a composite body between an ion conductive polymer and a nitrogen-containing compound and a fuel cell including the composite body. The nitrogen-containing compound has an immobilized portion to the ion conductive polymer and exhibits a resonance structure when protonated. The nitrogen-containing compound having a resonance structure when protonated is capable of assuming a chemical structure in which the multiple bond represented by the double bond is moved, with the atoms constituting the molecule not changing their positions.