PURPOSE: To enhance the mixing effect by utilizing density difference between liquid and gas and the centrifugal forces of both fluids, thereby crossing streams of both fluids.

CONSTITUTION: The device is provided with an outer cylinder 2, an inner cylinder 3 formed with a throttle part 3a having an inverse conical shape at the upper part in the outer cylinder 2, may narrow pores 3b formed in the inner cylinder 3, a liquid supply pipe 4 connected to the position opposited to the liquid supply pipe 4 in the tangent direction of the outer cylinder 2, and a gas supply pipe 5 connected in the tangent direction of the outer cylinder 2 towards the throttle part 3a of the inner cylinder 3.