A gas turbine combustor includes: an external cylinder (31); an inner cylinder (32) provided inside the external cylinder (31) to form an air passage (30) between the external cylinder (31) and the inner cylinder (32); a pilot nozzle (35) provided in a center part of the inner cylinder (32) along a direction of a combustor axis (S); a plurality of main nozzles (36) provided on an inner peripheral surface of the inner cylinder (32) along a circumferential direction thereof so as to surround the pilot nozzle (35), the plurality of main nozzles (36) premixing fuel with combustion air introduced to the air passage (30) and ejecting the fuel into the inner cylinder (32); and a top hat nozzle (41) provided inside the air passage (30) across a circumferential direction to mix fuel with the combustion air prior to reaching the plurality of main nozzles (36).