An ultrasonic transducer includes a substrate, a supporting film disposed on the substrate, and a piezoelectric element disposed on the supporting film. The substrate includes an opening. The piezoelectric element is disposed on an area that overlaps the opening in a plan view in a thickness direction of the substrate. A thickness of the supporting film at an area that overlaps the piezoelectric element in a plan view of the supporting film is smaller than a thickness of the supporting film at a different area different from the area that overlaps the piezoelectric element.