The aim of this research is to realize a small continuous flow system with emulsification devices. This system is designed for the generation of sub-micron or nano monodisperse emulsions. In this study, we have designed, fabricated, and evaluated a device that consists of a microchannel plate and an ultrasonic vibrating plate. This device can realize a continuous flow system and the plates are easily stacked. The oscillation frequency was 2.25 MHz. We succeeded in generating emulsions that have a diameter of 200 nm. We also designed the cross-sectional pattern of the microchannel of the ultrasonic device to increase residence time effectively. As a result, we have succeeded in obtaining emulsions that have a diameter of 80 nm. (C) 2011 The Japan Society of Applied Physics