A propulsion apparatus for a vessel includes a main screw and a push type POD propeller which is provided rearward of the main screw. Furthermore, a plurality of grooves which extend along flow directions of a hub vortex generated by the main screw are provided on a front end portion of a casing of the POD propeller. According to this propulsion apparatus for a vessel, the hub vortex generated by the main screw rearward of the main screw is weakened by diffusing the hub vortex along the grooves, and therefore the propulsion efficiency of the propulsion apparatus for a vessel is improved.