A gas turbine combustor comprising: a combustor outer casing; a combustor inner tube that is arranged within the combustor outer casing via an air passage; a top hat portion to which the combustor outer casing and the combustor inner tube are connected; a plurality of top hat nozzles that is arranged on the top hat portion along a circumferential direction of the top hat portion; a pilot nozzle that is arranged in a center area of the combustor inner tube; and a plurality of premix nozzles that is arranged on an inner circumference of the combustor inner tube along a circumferential direction of the combustor inner tube so as to surround the pilot nozzle, wherein the top hat portion includes: a top hat main body (61;101;111) that has a cylindrical shape and the top hat portion includes an inner ring (63;71;81) and an outer ring (64;72;82) that form a second fuel passage communicating with the first fuel passages (66; 102; 112) by being connected to the top hat main body (61; 101; 111) and being connected to each other; a fuel injecting unit being fixed to the inner ring (63;71;81) to communicate with the second fuel passage through a third fuel passage; characterised in that the top hat main body (61, 101; 111) has a plurality of first fuel passages (66; 102; 112) formed therein along an axial direction of the top hat main body (61; 101; 111); a cover that forms a cavity communicating with the first fuel passages (66;102;112) by covering a concave portion formed on the top hat main body (61; 101; 111); and a thermal elongation absorbing unit that is provided on at least one of the inner ring (63; 71; 81) and the outer ring (64;72;82) to absorb thermal elongation. a combustor outer casing; a combustor inner tube that is arranged within the combustor outer casing via an air passage; a top hat portion to which the combustor outer casing and the combustor inner tube are connected; a plurality of top hat nozzles that is arranged on the top hat portion along a circumferential direction of the top hat portion; a pilot nozzle that is arranged in a center area of the combustor inner tube; and a plurality of premix nozzles that is arranged on an inner circumference of the combustor inner tube along a circumferential direction of the combustor inner tube so as to surround the pilot nozzle, wherein the top hat portion includes: a top hat main body (61;101;111) that has a cylindrical shape and the top hat portion includes an inner ring (63;71;81) and an outer ring (64;72;82) that form a second fuel passage communicating with the first fuel passages (66; 102; 112) by being connected to the top hat main body (61; 101; 111) and being connected to each other; a fuel injecting unit being fixed to the inner ring (63;71;81) to communicate with the second fuel passage through a third fuel passage; characterised in that the top hat main body (61, 101; 111) has a plurality of first fuel passages (66; 102; 112) formed therein along an axial direction of the top hat main body (61; 101; 111); a cover that forms a cavity communicating with the first fuel passages (66;102;112) by covering a concave portion formed on the top hat main body (61; 101; 111); and a top hat main body (61;101;111) that has a cylindrical shape and the top hat portion includes an inner ring (63;71;81) and an outer ring (64;72;82) that form a second fuel passage communicating with the first fuel passages (66; 102; 112) by being connected to the top hat main body (61; 101; 111) and being connected to each other; a fuel injecting unit being fixed to the inner ring (63;71;81) to communicate with the second fuel passage through a third fuel passage; characterised in that the top hat main body (61, 101; 111) has a plurality of first fuel passages (66; 102; 112) formed therein along an axial direction of the top hat main body (61; 101; 111); a cover that forms a cavity communicating with the first fuel passages (66;102;112) by covering a concave portion formed on the top hat main body (61; 101; 111); a thermal elongation absorbing unit that is provided on at least one of the inner ring (63; 71; 81) and the outer ring (64;72;82) to absorb thermal elongation.