PURPOSE: To set an ultrasonic probe in the best state at any time by allowing at least either of a contactor and a vibrator to move freely so that the area of contacting between the contactor and vibrator is variable.

CONSTITUTION: The contactor 1 made of a flexible material such as silicone rubber has a conic projection 1A and is fitted in the hole 3 of a case 2. The vibrator 4 is put in the hole 6 of a fitting member 5 together with a damper 7 and its surface is covered with a front surface plate 8. When an ultrasonic analysis of the body is taken by using the contactor 1, the depth up to the echo generation point of an ultrasonic wave is measured previously and the member 5 is so rotated as to obtain the limit distance of a short-distance sound field, thereby increasing the area of the contactor 1 which is pressed against the vibrator 4. Then, the reverse surface of the contactor 1 is brought into contact with the skin surface of the body through a contact medium such as grease and an ultrasonic wave is transmitted into the body, so that the contactor 1 receives an echo from a position to be inspected with good sensitivity.