in an ultrasonic sensor having a case that is integrally constructed from tubular bodies , one end of each of which is open and the other end is closed by the bottom , and from a connection section for connecting the tubular bodies , and having piezoelectric elements individually provided on the inner bottom surfaces of the tubular bodies , reverberation caused by vibration of one of the piezoelectric element may affect the other piezoelectric element through the connection section . tubular bodies having the bottoms are connected through a connection section to portions of side surface sections near bottom sections , the portions being portions at which displacement by vibration of piezoelectric elements is minimum .