A fluorinated copolymer composition comprises ethylene/tetrafluoroethylene-containing copolymer and copper oxide. The ethylene/tetrafluoroethylene-containing copolymer comprises repeating units (A) based on ethylene, repeating units (B) based on tetrafluoroethylene and repeating units (C) based on another monomer, in a molar ratio of the repeating units (A) to the repeating units (B) of from 38/62 to 44/56, and in an amount of the repeating units (C) of from 0.1 to 2.6 mol % in all the repeating units of the ethylene/tetrafluoroethylene-containing copolymer. The content of the copper oxide is from 0.2 to 10 ppm based on the total weight of ethylene/tetrafluoroethylene-containing copolymer. The copper oxide has a BET surface area of from 5 to 30 m2/g. The volume flow rate of the fluorinated copolymer composition at 297° C. is from 15 to 150 g/10 min.