Abstract: The present invention provides flexibility in the shape and material of the cleaning vessel, enables high-power transmission of ultrasonic waves, and reduces audible noise generation. An ultrasonic cleaning machine according to the invention comprises an acoustic lens mounted above an ultrasonic transducer which is immersed in oil held within an external tank as well as a cleaning vessel holding a cleaning liquid further above the acoustic lens so that ultrasonic waves produced by the ultrasonic transducer converge at a point within the cleaning liquid. In one form of the invention, the cleaning vessel is eliminated and the cleaning liquid is held directly in the external tank.