In an observation method, measurement values of an object of measurement at a plurality of different positions in a plane that intersects a depth direction are acquired from an optical coherence tomography instrument (S100). In the observation method, measurement values are integrated in the depth direction at each of the plurality of positions (S104). In the observation method, a shrinkage parameter of the object of measurement is calculated on the basis of the integrated values at each of the plurality of positions (S105).