The invention provides an ultrasonic probe having a frame to constitute a part of a cubicle, a motor fixed on the frame, a first arm with one end fixed on a rotating shaft of the motor, and a second arm with one end rotatably coupled with the other end of the first arm via a coupling shaft and with the other end having an ultrasonic element mounted thereon. The second arm has a lengthwise long groove and is slidably engaged with the fixed shaft of the frame in the direction of length. The length from an end of the second arm where the ultrasonic element is mounted on the coupling shaft is designed to be longer than the length from the rotating shaft to the coupling shaft, and further, to be longer than the length from the rotating shaft to the fixed shaft.
