Abstract: A droplet oscillation device includes upper and lower electrodes, a changing mechanism, a sensor and a controller. The lower electrode is configured to support a substrate thereon. The changing mechanism is configured to change a distance between the upper and lower electrodes. The sensor is configured to detect a droplet formed above a surface of the substrate opposite the upper electrode. The controller is configured to vary an applied voltage between the upper and lower electrodes to oscillate the droplet, and to determine whether the droplet is detected by the sensor. The controller is configured to respectively determine whether the droplet is detected under a plurality of conditions for which a frequency of the applied voltage or the distance are different, and to oscillate the droplet at the frequency and the distance of a condition for which the droplet is detected and for which the distance is greatest.