A gas turbine control device includes a first estimation unit configured to estimate a first temperature which is a first turbine inlet temperature estimation value based on a first model which is a physical model using a fuel flow rate to a gas turbine; a second estimation unit configured to estimate a second temperature which is a second turbine inlet temperature estimation value based on a second model which is a physical model using an exhaust gas temperature of the gas turbine; and a correction unit configured to correct the first temperature based on the second temperature to calculate a third turbine inlet temperature estimation value.