Abstract: The present disclosure provides an ultrasonic transducer and a focused ultrasound treatment device. The ultrasonic transducer includes a sound generation unit and a sound emitting surface, the sound emitting surface being a spherical surface having a first notch, a second notch and a third notch, wherein one great circle of a sphere corresponding to the sound emitting surface is a main great circle, the first notch and the second notch are respectively positioned at two intersections of the spherical surface and a diameter perpendicular to the main great circle, and the third notch connects the first notch with the second notch; each cross-section of the sound emitting surface parallel to the main great circle is in a shape of an arc; and the ultrasonic wave generated by the sound generation unit is focused on a center of the sphere corresponding to the sound emitting surface.