Provided is a piezoelectric substrate, containing an elongate piezoelectric body that is helically wound, in which the piezoelectric body includes an optically active polypeptide, a length direction of the piezoelectric body and a main orientation direction of the optically active polypeptide included in the piezoelectric body are substantially parallel to each other, and the piezoelectric body has a degree of orientation F of from 0.50 to less than 1.00, as determined from X-ray diffraction measurement by the following Formula (a): DegreeoforientationF=α/180° in Formula (a), α represents a half width (°) of a peak derived from orientation.
