An ultrasonic water jet apparatus includes a water accumulation part in which the water supplied from a water supply source is temporarily accumulated, a jet port that jets the water accumulated in the water accumulation part, and a piezoelectric vibration plate including a dome part that is disposed opposed to the jet port in the water accumulation part and propagates the ultrasonic vibration to the water accumulated in the water accumulation part, a flange part that projects outward in the radial direction from a peripheral edge of the dome part, and an annular plate that projects outward in the radial direction from a peripheral edge of the flange part.