Provided is a compressor control unit with a high response ability to changes of gas condition of a compressor (compressor suction temperature, pressure, gas specific gravity, pressure ratio of suction pressure and discharge pressure). In the control unit for a compressor that supplies gas into a gas turbine through a header tank, an inlet gas condition is measured and a load command value from a gas turbine controller is corrected to be increased or decreased corresponding to the measured inlet gas condition.