Abstract: A transmitter- receiver of an ultrasonic distance measuring device comprising a cylindrical piezoelectric element made of a polymer in place of a piezoelectric vibrator of a ceramic material or the like which has heretofore been used. The cylindrical piezoelectric element is secured to a columnar supporter in such a manner as to define a chamber in cooperation with a recess which is provided in the peripheral surface of the supporter. The supporter is provided with a pressure equalizing bore which provides communication between the chamber and the outside. In addition, a conical reflector is provided so as to impart directivity to the ultasonic wave transmitted from the piezoelectric element.