In the sewage disposal plant and the fish fish farms and the closed waters of the ocean and the like, making use of the former vapor feeder, the vapor is made to melt in suffering processing underwater in high efficiency, and that processing water aeration method and the aerator and the aeration system which can be transported to another place in waterhead difference are offered. The suffering processing water (1W) the diffused air section which generates the air bubble grain in (22) with, the air bubble rise section where the group of the aforementioned air bubble grain which occurs rises (3P) with, as for the aforementioned air bubble grain from above water being pushed up on, by the fact that it changes in the liquid bubble, the suffering processing water (1W) to liquid membrane the processing water (2W) the liquid bubble water supply section which can be transported (5P) with it possesses the air bubble grain rise passage section which can convert (4P) with, with waterhead difference.
