To provide an inlet guide vane controller for a gas turbine which has a simple structure, improves output increase capability of the gas turbine, and increases frequency response capability of a gas turbine power generation unit.

In this inlet guide vane controller for operating an opening of an inlet guide vane based on a generator output signal to change an amount of air flowing into the gas turbine, an amount of increase of generator output corresponding to an amount of increase of a fuel control signal is inferred and computed, and the inferred amount of increase of output is added to the generator output signal to set an opening of the inlet guide vane based on it.