To provide a gas turbine and its operating method, suppressing lowering in performance of a compressor and assuring original effect of increase in output, in spraying droplets into intake air.

The gas turbine burning compressed air refined by a compressor 2 to generate rotating power, comprises: a spray device 10 properly spraying the droplets into the intake air 1 of the compressor 2; an extraction line 12 extracting air that is being compressed in the compressor 2; an extraction valve disposed to the extraction line 12; and a control device 18 controlling the extraction valve 14 so that the sprayed droplets are purged from the compressor 2 through the extraction line 12 at least immediately after the spray until a set time has elapsed, in spraying the droplets from the spray device 10.