A method for measuring an internal temperature of a freezing target object includes: a placing step of placing the freezing target object in a microwave resonating magnetic field generated by a microwave resonator; a state detection step of detecting a resonant state of the freezing target object in a frozen state by using the microwave resonator and detecting an internal temperature of the freezing target object by using a temperature meter; a calibration curve calculation step of calculating a calibration curve by performing a regression analysis by using the resonant state as an explanatory variable and by using the internal temperature of the freezing target object as a response variable; and a temperature calculation step of calculating the internal temperature of the freezing target object in the frozen state by applying the resonant state detected in the detection step to the calibration curve calculated in the calibration curve calculation step.
