The purpose of this study is searching for a new method of dispersing spilled heavy oil, which has a detrimental effect on the natural environment and the ecosystem of the sea. A method ejecting a water jet vertically downward to heavy oil on the water surface was discussed. The water jet involved the heavy oil and the minute air bubbles, when it hits oil layer on water surface and passed the nozzle of a horizontal underwater guide plate. The shape of nozzles of the guide plate was three types; a conventional nozzle, a 5 times longer nozzle, and a taper nozzle. The dispersion efficiency of the taper nozzle was the best among three. The flow in the three nozzles was recorded by a high-speed camera. From the high-speed movies, the occurrence of two flows, normal and counter flow, was suspected in the taper nozzle. It seemed that the two flows (normal and counter flows) incresesed the sharing force between the minute air bubbles. It is considered that the sharing force increased the efficiency of disperse oil.