A gas turbine combustor comprising: a chamber for mixing and burning supplied fuel and supplied air to generate combustion gas; an air hole plate located in an upstream side of the chamber, forming a plurality of air holes for supplying the air; a plurality of fuel nozzles for supplying the fuel to the plurality of air holes formed in the air hole plate, wherein the air holes are disposed in the downstream side of the fuel nozzles that each of the fuel nozzles is paired with one of the air holes; and a plurality of burners made up of the plurality of air holes and the plurality of fuel nozzles in pairs, wherein the plurality of burners comprises a center burner disposed on an axis of the gas turbine combustor and a plurality of outer burners installed around the center burner, the center burner is fixed to a first fuel supply system for supplying the fuel to the fuel nozzles in the center burner, the plurality of outer burners is fixed to a second fuel supply system for supplying the fuel to the fuel nozzles in outer burner's inner portions which are inner regions of specific outer burners among the outer burners, the plurality of outer burners is fixed to a third fuel supply system for supplying the fuel to the fuel nozzles in outer burner's inner portions which are inner regions of outer burners other than the specific outer burners, the plurality of outer burners is fixed to a fourth fuel supply system for supplying the fuel to the fuel nozzles in outer burner's outer portions which are outer regions of the outer burners, a fuel rate adjusting valve (61, 62, 63, 64) is provided with the first fuel system, the second fuel system, the third fuel system, and the fourth fuel system, respectively, and a control device is provided to adjust the flow rate of the fuel supplied through each of the fuel systems (51, 52, 53, 54) by changing the opening of the fuel rate adjusting valve (61, 62, 63, 64), wherein the control device is constructed to control the fuel rate adjusting valve (61, 62, 63, 64), and the control device is further constructed to send a control signal to the fuel rate adjusting valve provided with the first fuel system so that the fuel is supplied through the first fuel supply system to the fuel nozzles disposed in the center burner when the gas turbine is operated in a low load operation mode A, and a control signal to the fuel rate adjusting valve provided with the second fuel system so that the fuel is additionally supplied through the second fuel supply system to the fuel nozzles disposed in the outer burner's inner portions which are the inner regions of the specific outer burners among the plurality of outer burners when the gas turbine is operated in a partial load operation mode B with increased load regarding the low load operation mode A, and a control signal to the fuel rate adjusting valve provided with the third fuel system so that the fuel is additionally supplied through the third fuel supply system to the fuel nozzles disposed in the outer burner's inner portions which are the inner regions of all other outer burners among the plurality of outer burners except for the specific outer burners when the gas turbine is operated in a partial load operation mode C with increased load regarding the partial load operation mode B, and a control signal to the fuel rate adjusting valve provided with the fourth fuel system so that the fuel is additionally supplied through the fourth fuel supply system to the fuel nozzles disposed in the outer burner's outer portions which are the outer regions of all the outer burners when the gas turbine is operated in a full load operation mode D with increased load regarding partial load operation mode C.