In a method of evaluating a piezoelectric field, non-destructive spectrometry of piezoelectric fields is performed in a semiconductor heterojunction using a technique different from PR spectroscopy. In the method, at first, first and second absorption spectra are measured by irradiating the sample with infrared light at first and second angles, respectively. Then, a peak position of an absorption band having incident-angle dependent intensity is specified, based on the first and second absorption spectra. Thus, the piezoelectric field strength is obtained using a relationship between the piezoelectric field and an electron energy level corresponding to the peak position.