In this study, a new micro bubble generator, i.e. nozzle, with a very simple construction is proposed newly and the behavior, such as velocity distribution and spread, of micro bubble jet flow is made clear by PIV and LDA measurements of velocity distribution. The new nozzle uses a very high velocity water jet flow having a large velocity gradient near the nozzle exit. The shearing force shears the gas bubbles and makes considerable small bubbles or rather micro bubbles. The aeration characteristics of this micro bubble generator, i.e. nozzle, are also discussed.