PURPOSE: A rudder for a ship is provided to increase performance by reducing gap variations by forming a guide part on the back end of a rudder horn. CONSTITUTION: A rudder for a ship comprises a rudder horn(110), a rudder moving unit(130), and a guide unit(115). The rudder moving unit is installed on the rudder horn in order to rotate. The guide unit is installed in both back-end sides of the rudder horn. The guide unit circulates fluid along the side of the moving unit by preventing the inflow of fluid into a gap between the rudder horn and a rudder operating unit. One side of the guide unit is located on the rudder horn and the other side is expanded toward the moving unit.
