In a temperature estimation apparatus for an aeroplane gas turbine engine mounted on an aircraft and having a combustion chamber, a high-pressure turbine rotated by combustion gas exhausted from the combustion chamber, a low-pressure turbine located downstream of the high-pressure turbine to be rotated by low-pressure gas which has passed through the high-pressure turbine, a high-pressure turbine rotational speed sensor, a low-pressure turbine rotational speed sensor, and a temperature sensor, inlet temperature at an inlet of the high-pressure turbine is estimated based on the detected outlet temperature of the low-pressure turbine and the rotational speed of the low-pressure turbine and is corrected with the detected rotational speed of the high-pressure turbine.