To provide an ultrasonic diagnostic system which enables the focusing of ultrasonic waves on the focal position of a lens with the surface of the lens on the sectional surface parallel with the center axis of rotation of a cap including the center of the sound axis of the ultrasonic waves and the surface of the lens on the sectional surface orthogonal to the center axis and miminizes the deviation from the focal position depending on neither the cap nor an acoustic medium.

The system includes the cap and the lens 63 provided on a piezoelectric element 61 while including an ultrasonic oscillator provided within the cap 24 freely rotatable with the center of the cap as the center axis of rotation and the acoustic medium filling the cap. The lens 63 collects the ultrasonic waves radiated from the piezoelectric element 61 while having a shape of making the first focal range L1 of the first lens surface 71 on the sectional surface parallel with the center axis of rotation containing the center S of a sound axis of the ultrasonic waves shorter than the second focal range L2 of the second lens surface on the sectional surface orthogonal to the center axis of rotation including the center S of the sound axis.