To defoam even a liquid such as a photographic emulsion and also to avoid flocculation of an additive by transferring ultrasonic vibration of a frequency change cycle changing from vibration of low frequency to that of high frequency by one frequency change cycle or more.

Drive control is performed in such a manner that after an oscillator drive controller 8 vibrates an ultrasonic vibrator transducer 7 at the minimum frequency for several seconds every frequency, the vibration is carried out at a high frequency, and after vibration at a low frequency, the vibration is carried out at a high frequency. A photographic emulsion is prepared in a liquid storage tank 1, and heated water is passed through a jacket 6, and the transducer 7 is vibrated by the oscillator drive controller 8 for 30min by making one cycle of 28kHz→45kHz→100kHz for 5sec every frequency 15sec, allowing ultrasonic vibration to be transferred to the photographic emulsion in the liquid storage tank 1 to perform defoaming. As a result, a photographic emulsion in which defoaming is complete and the flocculation of an additive is eliminated is obtained, and the emulsion thus obtained is uniformly applied to a photosensitive material base.