To the ultrasonic transmission direction of the ultrasonic sending and receiving device reflection of the ultrasonic rear which is emitted on opposite side is decreased, high resolution in order to obtain the ultrasonic diagnostic picture, on the baseplate, insulating layer and the aforementioned cavity and put insulating layer the higher stratum of society electrode and the lower stratum electrode which put the cavity and the aforementioned cavity are provided and the ultrasonic vibrating element is formed, the aforementioned baseplate is kept through the elastic member to the backing low, direct current voltage and alternating current volts are impressed between the aforementioned electrodes, in the ultrasonic probe which the ultrasonic vibrating element vibrates, the aforementioned baseplate and the description above low the machine impedance which consists of the elastic member and,Acoustic impedance of the backing is designated as the same value in general.超音波送受信デバイスの超音波送信方向とは反対側に放射される超音波の背面の反射を低減し、高解像な超音波診断画像を得るために、基板上に、空洞と、前記空洞を挟む絶縁層と、前記空洞と絶縁層を挟む上層電極と下層電極を設けて超音波振動素子を形成し、前記基板をバッキングに低弾性部材を介して保持し、前記電極間に直流電圧と交流電圧を印加して、超音波振動素子を振動させる超音波探触子において、前記基板と前記低弾性部材から成る機械インピーダンスと、バッキングの音響インピーダンスとを概ね同じ値とする。
