The present invention provides an ETFE-type copolymer having a high melt tension and excellent blow moldability. An ethylene-tetrafluoroethylene copolymer which comprises ethylene units, tetrafluoroethylene units and units of a monomer (A) having at least two copolymerizable double bonds and which has a ratio (X/W) of its melt tension (XmN) to a load (Wkg) applied for the measurement of the melt tension being at least 0.8.