All the ultrasonic transducers constituting the ultrasonic transducer group 48 of the ultrasonic transmission / reception unit 14 are connected to the wiring board 49 and the electric wiring 50, respectively, so that all the ultrasonic transducers can transmit / receive ultrasonic waves. For this reason, it is assumed that the second ultrasonic transducer group 48b in which the ultrasonic waves are reflected in the housing 41 is generated due to the shape (inclination, protrusion amount) and the influence of the outer peripheral portion 42a of the opening 42 of the housing 41. In addition, it is possible to appropriately secure the first ultrasonic transducer group 48 a that can emit ultrasonic waves from the opening 42.超音波送受信部１４の超音波振動子群４８を構成する全ての超音波振動子を、それぞれ、配線基板４９と電気配線５０で接続して、全ての超音波振動子が超音波の送受信ができるようにしたため、たとえ、ハウジング４１の開口部４２の外周部４２ａの形状（傾き、突出量）や影響等により超音波がハウジング４１内で反射する第２の超音波振動子群４８ｂが生じたとしても、超音波が開口部４２から射出できる第１の超音波振動子群４８ａを適切に確保できる。
