A piezoelectric substrate , comprising: a conductor cord that has a core material and a conductor disposed around the core material; and an elongated piezoelectric body that is disposed around the conductor cord in a spiral manner, unidirectionally along an axial direction of the conductor cord, wherein: the piezoelectric body comprises an optically active helical chiral polymer, a lengthwise direction of the piezoelectric body and a main orientation direction of the helical chiral polymer in the piezoelectric body are substantially parallel to each other, the piezoelectric body has an orientation degree F of from 0.5 to less than 1.0, as determined by X-ray diffractometry and Formula (a): F = (180° - α)/180°, wherein α represents a half width of a peak derived from orientation, and when the conductor cord is viewed from a direction perpendicular to an axial direction of the conductor cord, the conductor cord satisfies Formula (b): ΔD max < t pmin , wherein ΔD max is a maximum value of a difference in height between a division A that is selected from plural divisions and a division B that is adjacent to the division A, and t pmin is a minimum thickness of the piezoelectric body. a conductor cord that has a core material and a conductor disposed around the core material; and an elongated piezoelectric body that is disposed around the conductor cord in a spiral manner, unidirectionally along an axial direction of the conductor cord, wherein: the piezoelectric body comprises an optically active helical chiral polymer, a lengthwise direction of the piezoelectric body and a main orientation direction of the helical chiral polymer in the piezoelectric body are substantially parallel to each other, the piezoelectric body has an orientation degree F of from 0.5 to less than 1.0, as determined by X-ray diffractometry and Formula (a): F = (180° - α)/180°, wherein α represents a half width of a peak derived from orientation, and when the conductor cord is viewed from a direction perpendicular to an axial direction of the conductor cord, the conductor cord satisfies Formula (b): ΔD max < t pmin , wherein ΔD max is a maximum value of a difference in height between a division A that is selected from plural divisions and a division B that is adjacent to the division A, and t pmin is a minimum thickness of the piezoelectric body. the piezoelectric body comprises an optically active helical chiral polymer, a lengthwise direction of the piezoelectric body and a main orientation direction of the helical chiral polymer in the piezoelectric body are substantially parallel to each other, the piezoelectric body has an orientation degree F of from 0.5 to less than 1.0, as determined by X-ray diffractometry and Formula (a): F = (180° - α)/180°, wherein α represents a half width of a peak derived from orientation, and when the conductor cord is viewed from a direction perpendicular to an axial direction of the conductor cord, the conductor cord satisfies Formula (b): ΔD max < t pmin , wherein ΔD max is a maximum value of a difference in height between a division A that is selected from plural divisions and a division B that is adjacent to the division A, and t pmin is a minimum thickness of the piezoelectric body. <EOS>