Conventionally, we have removed small particles in muddy water mainly by using 　agglomerating medicine and filter. In place of this conventionally method, we carried out research by utilizing radiation pressure of ultrasonic. We produced experimental devices that occurs pseudo standing waves by ultrasonic. We succeeded to cause the small particles in muddy water to agglomerate and transport. Through the experiments, we researched characteristics of agglomerating and transporting the small particles. We clarified the following by the experiment. There is a big transition between the inflow speed and processing capability when certain speed(threshold velocity)gets over. The threshold velocity does notrely on initial turbidity. The transporting speed of flocks which is made of ag-glomerated small particles become first, as the inputted power is high. When ul-trasonic(frequency 2MHz, input power 200W, diameter of small particlesφ7.9μm)was inputted, muddy water contains diameter 7.9μm particles became clean water at the speed of 4.2 ml/sec to 50ppm. In this examination, the device couldn't process so much quantity of muddy water. We need more research in order to raisethe system efficiency furthermore. However, we have been able to show the possi-bility of a new muddy water processing system without medicine and a filter.