The present invention comprises: a fixed unit fixated to and installed in a ship body; and a rudder installed to be rotated in the fixed unit. The rudder comprises: a first rudder wherein a front edge part side disposed to face a propeller to be tilted in a port direction based on a center line in the width direction; a second rudder disposed in a lower portion of the first rudder and wherein the front edge part side is tilted in the startboard direction based on the center lined in the width direction; a slope unit connecting the first and the second rudder; and a negative pressure generation preventing unit disposed to surround the slope unit.
