Provided is a multi-tube nozzle for use in eradicating harmful aquatic organisms, which physically kills harmful aquatic organisms while feeding water and thus allows intake water to be fed directly into a culture tank or a ballast tank without the need for a pretreatment tank, chemicals, neutralizers, etc. A multi-tube nozzle (A) for use in eradicating harmful aquatic organisms includes at least three nozzle tubes (1) that are provided adjacent to each other. The nozzle tubes (1) each includes: an inlet-side opening section (2) having an inner diameter that decreases from an inlet opening toward a throat section (3) located in the middle of the tube; an outlet-side opening section (4) having an inner diameter that increases from the throat section (3) toward an outlet opening; and the throat section (3) having a smallest inner diameter. The adjacent nozzle tubes (1) are spaced apart by a distance such that the adjacent inlet-side opening sections (2) overlap each other. A wall (5) of an overlapping portion (6) of the inlet-side opening sections (2) is cut in a U shape. An uncut portion (5a) between the adjacent U-shaped cut portions (5b) forms a sword-like pointed tip.