Provided is a gas turbine operation control device and operation control method that are capable of suppressing turbine inlet temperature and of satisfying the demand response for shaft output. An IGV emergency fully-open flag is activated when the output of a generator is in a high load band at or above a predetermined value, and the like. When the IGV emergency fully-open flag is activated, the degree of opening of an inlet guide vane is set to a predetermined degree of opening, a temperature adjustment setting is set by switching in accordance with the degree of opening of the inlet guide vane, and an exhaust gas temperature setting value or a blade path temperature setting value of a turbine, for controlling the fuel supply amount for a combustor, is generated based on the temperature adjustment setting.