Ethylene-vinyl alcohol copolymers have superior gas barrier properties, but are inferior in bending fatigue resistance. The present invention improves bending fatigue resistance without reducing the gas barrier property and heat resistance. An ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 50 percent by mole is modified by incorporating 0.01 to 1% mol of a structural unit expressed by the following formula (3): wherein, n indicates an integer of 2 to 5, m indicates an integer of 10 to 20, and R1 indicates a C1 to C20 aliphatic hydrocarbon group provided that R1 may contain a mercapto group, thioester group, sulfenamide, vinyl group, methacryloxy group, or acryloxy group. The modified ethylene vinyl alcohol copolymer may be used as a gas barrier resin and this gas barrier resin may be shaped or laminated and used in various applications such as in pneumatic tires and hoses.