The present invention provides a method of measuring the internal temperature of a frozen object that can accurately measure the internal temperature of frozen assorted food. The method of measuring the internal temperature of a frozen object, which includes a plurality of assorted frozen foods having a granular shape in which the outer side of the inner edible part is covered with a skin, comprises: an arrangement step for arranging a frozen object in a microwave resonance electromagnetic field generated in a microwave resonator; a state detection step for detecting the resonance peak voltage and resonance frequency of the frozen object by the microwave resonator and detecting the internal temperature of the frozen object by a temperature measurement device; a calibration curve calculation step for calculating a calibration curve by performing regression analysis using the resonance peak voltage and resonance frequency detected in the state detection step as explanatory variables and the internal temperature
