An intracranial pressure estimating method includes: an acquisition step (S10) of acquiring time-series data on external ear canal pressure pulse waves of a subject; an analysis step (S12) of analyzing external ear canal pressure pulse wave data obtained by digitalizing the time-series data on the external ear canal pressure pulse waves, to calculate a first formant frequency of the external ear canal pressure pulse wave data; a correction step (S13) of correcting the calculated first formant frequency based on personal information on the subject to calculate a corrected value; and an estimation step (S14) of calculating an estimated value of an intracranial pressure based on the calculated corrected value.