There is provided a piezoelectric stack, including: a substrate; an output-side bottom electrode film on the substrate; an output-side piezoelectric film, being an oxide film, on the output-side bottom electrode film; an output-side top electrode film on the output-side piezoelectric film; an input-side bottom electrode film on the substrate; an input-side piezoelectric film, being a nitride film, on the input-side bottom electrode film; an input-side top electrode film on the input-side piezoelectric film; and an ultrasonic output part and ultrasonic input part placed in such a manner as not overlapping each other when viewed from a top surface of the substrate, the ultrasonic output part comprising a stacked part of the output-side bottom electrode film, the output-side piezoelectric film, and the output-side top electrode film, the ultrasonic input part comprising a stacked part of the input-side bottom electrode film, the input-side piezoelectric film, and the input-side top electrode film.