An ultrasonic dog beater comprises an upper shell 10, a lower shell 10 and an ultrasonic oscillation circuit board 30, and is characterized in that the upper shell 10 is divided into two halves, the left half is a rectangular battery cover 12, and the battery cover is provided with a screw hole seat 14, and the right half is a rectangular battery cover. There is also a small round hole 18 on the right. The top surface of the upper housing 10 has a screw hole seat 14 and a protruding column 24. The convex column 24 is arranged below the contact opening 16, and the inner wall is provided with a flange 32. The edge of the inner wall is provided with two symmetrical slots 26 and two symmetrical clips 28, which are formed on the edge of the wall between the two clips 28. The lower housing 20 is also divided into two halves, wherein the left half is rectangular and the right half is trapezoidal. The inner wall is provided with a concave edge 36, and two pairs of engaging pieces 38 and 42 corresponding to the engaging grooves 26 and 28 of the upper housing are provided on the inner wall edge. The wall edges between the engagement grooves 42 also form a concave semi-circular arc 44, and form an arc corresponding to the semi-circular arc 34 of the upper housing 10. The ultrasonic oscillation circuit board 30 is composed of a non-hidden multivibrator circuit, including a timer 1C, a capacitor C5, a transformer T 1, an amplifier crystal Q 1 and an LED. The circuit board 30 is provided with three circular holes 52.