Propellers having strong skew-back blades are often seen in small fishing boats. Generally speaking, two advantages can be attained by skewing back propeller blade tips. The one is that we can lessen the bad effect of aft body of ship upon the propeller; i. e . the propeller can avoid encountering high wake simultaneously from tip to root in the center line plane of ship. The other advantage is that we can avoid cavitation to a certain extent by making flow path along the blade surface longer. Now in this paper the author has investigated by tests the influence of skew-back from the air-drawing point of view. The result is that, although the influence of skew-back may be little in ordinary mercantile propellers having a little skew-back, large skew-back is detrimental from the air-drawing point of view to say nothing of strength and efficiency.