A hydrogen content fuel can be stably ignited using a gaseous fuel that does not contain hydrogen and dispersibility of the hydrogen content fuel is enhanced.
A gas turbine combustor including a burner including: a startup fuel pipe in which a startup fuel circulates; a first main fuel pipe in which a main fuel circulates, a second main fuel pipe in which the main fuel circulates; a fuel mixer to which the startup fuel pipe and the first main fuel pipe are connected; an inner fuel nozzle to which the fuel mixer is connected; a plurality of outer fuel nozzles to which the second main fuel pipe is connected; a startup fuel control valve provided in the startup fuel pipe; a first fuel control valve provided in the first main fuel pipe; and a second fuel control valve provided in the second main fuel pipe.