To provide an aeration system capable of economically aerating simply without much equipment cost even in a wide range of water zone and further preventing contamination and pollution of the water zone on dredging.

The aeration system is constituted of an onboard aeration water ejection device, a water ejection nozzle arranged in water, and piping connecting between the aeration water ejection device and the ejection nozzle. The high pressure water supplied by the pump is changed into an air-mixed water stream by the aeration water ejection device, and ejected as a high pressure water stream consisting of water including fine air bubbles into water through the nozzle.