Abstract: A dispersion/stirring apparatus that is capable of micronizing gas dispersed and stirred into a liquid in a tank without requiring a separate pump or a stirring device is provided. The rotation unit is provided with a flow path that opens at an inner diameter side as well as an outer diameter side of the rotation unit. The flow path is provided with a flow path expansion portion at which the flow path expands in the direction towards the outer diameter side of the rotation unit. The flow path expansion portion of the rotation unit has an effect similar to that of a Venturi tube and thereby enables micronization of a gas. Rotation of the rotation unit produces a pump effect and a stirring effect, thereby eliminating the need of providing a separate pump or stirring device.