The atomization behavior of a single droplet impinged on a surface oscillating with ultrasonic frequency of 20 kHz was investigated as a new method of fine-spray formation. Distilled water, ethanol, and a glycerin solution were used as the test liquids to clarify the effects of surface tension and viscosity on the ultrasonic atomization. Also, the effects of amplitude of oscillation and droplet volume on the ultrasonic atomization were investigated. As a result, it was found that a fine spray could be formed by the droplet impingement to an oscillating surface when the amplitude was <= 50 mu m, while some ligaments and large droplets were formed at >50 mu m amplitude. The Sauter mean diameter (SMD) of the spray formed after the impingement was approximately D-32 = 70 Pm for small amplitudes, but the SMD became large with an increase of the amplitude. At a small amplitude of 25 pin, the surface energy of the spray after impingement increased remarkably compared with that of the single droplet before impingement. Thus, the small amplitude of oscillation could allow the formation of a fine spray by disintegrating the liquid film formed after the droplet impingement. On the contrary, at large amplitudes of >50 mu n, the kinetic energy of the spray after impingement exceeded the surface energy; namely, the oscillation energy acted on the rebounding rather than the atomization of the droplet. The atomization efficiency decreased exponentially with an increasing of the amplitude of oscillation regardless of the physical properties of the liquids.