The present invention relates to a rudder for a ship. The rudder for a ship is installed behind a propeller to control a sailing direction of a ship, and comprises: a rudder body; and a rudder bulb protruding from a front end of the rudder body. The rudder bulb comprises: a convex portion whose outer surface is convexly formed in an outward direction of a central axis; and a concave portion whose outer surface is concavely formed in an inward direction of the central axis. The rudder for a ship forms the convex portion on the rudder bulb towards the outside in a prescribed angle range including an upper end of a left side and a lower end of the right side, and forms the concave portion on the remaining portion to reduce a hub vortex and minimize friction resistance. Also, the rudder for a ship disposes the convex portion on a portion where a reduction of a hub vortex is needed due to a relatively high flow rate, and connects the streamlined concave portion to the remaining portion to suppress an increase in resistance.
