An annular type gas turbine combustor having a plurality of fuel nozzle assemblies (10) on a circumference includes a pilot nozzle unit (12) for spraying a fuel for diffusive combustion from a pilot outer peripheral nozzle (34) into a combustion chamber (8), a main nozzle unit (14) provided so as to surround the pilot nozzle unit (12) for spraying a fuel for premix combustion, and a flow guide (27) disposed on a downstream side of each of the fuel nozzle assemblies (10) and having a sectional area of a passage for air and air-fuel mixture from each of the fuel nozzle assemblies (10), which gradually increase in a downstream direction.