PURPOSE: To suppress noise by forming flat notches formed out of a plurality of triangular surfaces disposed along at least a part of respective surfaces adjacent to the trailing edge in at least one of main surfaces almost without interfering with the contour of a trailing edge.

CONSTITUTION: In the propeller blade 1 of a hydrofoil, noise caused by vortex shedding generated at a trailing edge is suppressed by arranging notches 4 in a row 5 along the main surface 6 of the blade adjacent to the trailing edge. A row 7 similar to triangular notches 8 is formed along the back side surface 9 of the blade adjacent to the trailing edge. The notches 4 and 8 serve to interrupt the regular characteristics of vortex shedding, thus suppressing or inhibiting noise. The surfaces of the respective notches are flat, and the notches are continuous, therefore, no flat areas are at the surfaces 6 and 9 between adjacent notch corners. The two rows 5 and 7 of the notches 4, 8 are shifted sequentially each other, and the notch of one surface 6 of the blade is in a space to the other surface 9.