An ultrasonic sensor which includes a substrate where an opening section is formed, a vibration plate that is provided on the substrate so as to close the opening section, and a piezoelectric element that is layered on a surface of the vibration plate on an opposite side to the opening section and includes a first electrode, a piezoelectric element, and a second electrode, includes a reflection layer that is provided in a space around the piezoelectric element on the surface of the vibration plate on an opposite side to the opening section, to reflect other ultrasonic waves which are transmitted in a different direction from a transmitted ultrasonic wave transmitted to a measuring target side on an interface between the piezoelectric element and the reflection layer, and has a thickness so as to superimpose other ultrasonic waves on the transmitted ultrasonic wave.