A gas turbine combustor comprising: a diffusion burner for a diffusion combustion scheme; a diffusion gas control valve provided in a diffusion fuel system for the diffusion burner; a premixed burner for a premixed combustion scheme; at least one premixed gas control valve (21B-21E) provided in a premixed fuel system (20B-20E) for the premixed burner; a combustion liner that forms a combustion chamber downstream, in a fuel injection direction, of the diffusion burner and the premixed burner; and a control device that controls the diffusion gas control valve and the premixed gas control valve, wherein the premixed burner includes: a burner liner that surrounds the diffusion burner; a burner casing that surrounds the burner liner; a plurality of vanes that separate a cylindrical space between the burner liner and the burner casing into a plurality of premixers arranged side by side in a circumferential direction; a plurality of premixed fuel nozzles that are connected to the premixed fuel system and that inject a premixed fuel to the corresponding premixers; and at least one thermometer, wherein the control device is configured, in a case in which a detection value of the thermometer or an increase rate of the detection value exceeds a corresponding set value, to execute premixed fuel ratio control to reduce an opening of the premixed gas control valve and to increase an opening of the diffusion gas control valve in such a manner that a sum of flow rates of fuels supplied to the diffusion burner and the premixed burner remains unchanged, and characterized in that the at least one thermometer is installed to be buried in one of the vanes. a diffusion burner for a diffusion combustion scheme; a diffusion gas control valve provided in a diffusion fuel system for the diffusion burner; a premixed burner for a premixed combustion scheme; at least one premixed gas control valve (21B-21E) provided in a premixed fuel system (20B-20E) for the premixed burner; a combustion liner that forms a combustion chamber downstream, in a fuel injection direction, of the diffusion burner and the premixed burner; and a control device that controls the diffusion gas control valve and the premixed gas control valve, wherein the premixed burner includes: a burner liner that surrounds the diffusion burner; a burner casing that surrounds the burner liner; a plurality of vanes that separate a cylindrical space between the burner liner and the burner casing into a plurality of premixers arranged side by side in a circumferential direction; a plurality of premixed fuel nozzles that are connected to the premixed fuel system and that inject a premixed fuel to the corresponding premixers; and at least one thermometer, wherein a burner liner that surrounds the diffusion burner; a burner casing that surrounds the burner liner; a plurality of vanes that separate a cylindrical space between the burner liner and the burner casing into a plurality of premixers arranged side by side in a circumferential direction; a plurality of premixed fuel nozzles that are connected to the premixed fuel system and that inject a premixed fuel to the corresponding premixers; and at least one thermometer, wherein the control device is configured, in a case in which a detection value of the thermometer or an increase rate of the detection value exceeds a corresponding set value, to execute premixed fuel ratio control to reduce an opening of the premixed gas control valve and to increase an opening of the diffusion gas control valve in such a manner that a sum of flow rates of fuels supplied to the diffusion burner and the premixed burner remains unchanged, and characterized in that the at least one thermometer is installed to be buried in one of the vanes.