A vibrating piece manufacturing method includes: (a) preparing a supporting body having first and second surfaces, the first and second surfaces defining a thickness while being directed toward opposite directions, the supporting body including a base and a plurality of arms, the arms extending side-by-side in a direction orthogonal to a direction of the thickness from the base, a lower electrode film being disposed on the first surface of each of the arms, a piezoelectric film being disposed on the lower electrode films, at least one upper electrode film being disposed on the piezoelectric film, at least a part of the second surface of each of the arms being an exposed area; and (b) etching the exposed area of the second surface so as to reduce the thickness to reduce flexural rigidity of the arms with respect to the thickness direction.