PURPOSE: To give a sharp directional characteristic and high transmission/ reception sensitivity characteristic by sticking an annular thin plate to an annular piezoelectric element.

CONSTITUTION: An annular piezoelectric element 11 is stuck to an inner bottom of an annular plate having a V-shaped section for including a normal for passing through the center of a circle. Parabolic-surface hones 20 and 21 are provided inside and outside the thin plate 13 through an elastic rubber 22, etc. Then, the titled receiver shows the directional characteristic similar to a circular piston sound source. As a result, it shows the narrower directivity compared with a conventional one even if a ultrasonic wave emitting area is equal.