<p>A dispersion/stir device (11) disperses and stirs gas in liquid in a tank (66) and can break the gas into fine bubbles. The device (11) achieves this without additionally requiring a pump and a stirring device. A rotation body (13) is provided with a flow path (53) open to both the inner diameter side and the outer diameter side of the rotation body (13). In the flow path (53) is provided an expanded flow path section (56) where the space of the flow path (53) expands from the inner diameter side to the outer diameter side. The expanded flow path section (56) has a similar effect to a venturi tube and can break gas into fine bubbles. Rotation of the rotation body (13) provides a pumping effect and a stirring effect, which eliminates the need of an additional pump and an additional stirring device.</p>
