In a temperature estimation apparatus for an aeroplane gas turbine engine, there are provided with a calculator that calculates a low-pressure turbine outlet temperature change (dEGT) based on low-pressure turbine rotational speed (N1) and ambient temperature (T1), a calculator that calculates a model outlet temperature (MODEL-EGTC) based on corrected high-pressure turbine rotational speed (N2C) and atmospheric pressure (P0) to calculate a model outlet temperature difference (dEGTC) by subtracting the calculated temperature (MODEL-EGTC) from a corrected low-pressure turbine outlet temperature (EGTC), a calculator that calculates a correction amount (dEGTad) relative to the model outlet temperature difference (dEGTC) based on the model outlet temperature difference (dEGTC) and low-pressure turbine rotational speed (N1), and a calculator that calculates an estimation value of the low-pressure turbine inlet temperature (ITT) based on the low-pressure turbine outlet temperature (EGT), etc., thereby enabling to estimate the inlet temperature of the low-pressure turbine.