Provided is an ethylene/tetrafluoroethylene copolymer having high heat resistance and having excellent crack resistance even when used in a high-temperature environment. Said copolymer contains ethylene, tetrafluoroethylene, and the fluorine-containing vinyl monomer copolymer unit represented by the general formula CH2=CH-Rf (Rf representing a perfluoroalkyl group containing at least four carbon atoms). The copolymer is characterized in that the fluorine-containing vinyl monomer constitutes 0.8 to 2.5 mol% of the total of all the monomers, the molar ratio of ethylene to tetrafluoroethylene is between 33.0:67.0 and 44.0:56.0, the CH index is at most 1.40, the melting point is at least 230 DEG C, and the melt flow rate is at most 40 g/10 min.