In this report discussed are the shallow water effects on the ship's hull torudder interaction on the same assumption as in the previous report that the main hull and the rudder can be replaced by rectangular flat plates placed in a line. However, the spanwise distribution of vorticity on the rudder is simplified to be constant in each of equal sections into which the total length of rudder's span is divided for convenience of numerical analysis. In conse-quence of this simplification, the computing time necessary to solve the integral equations which determine the vorticity distribution of the main hull and the rudder could be reduced remarkably. From the results of numerical calculation, it is concluded that the hydrodynamic force induced on the main hull by deflecting the rudder increases as the water depth decreases. This conclusion is confirmed by quantitative agreement with the results of experiments in shallow water carried out recently by Nonaka and others. On the contrary, the hydrodynamic force of the rudder behind the main hull does not monotonously increase as the water depth decreases, but it may be less than that in infinitely deep water. The conclusion obtained in the previous report that the hydrodynamic force acting on the rudder itself is reduced by the presence of the main hull, however, remains true still in shallow water. The effectiveness of the rudder as a means to keep a ship on her course and to make a ship turn is evaluated by the amount of the total force generated on the main hull and the rudder. The results of numerical calculation indicate that from the viewpoint just stated above the rudder effectiveness increases with decrement of the water depth. Besides, this conclusion agrees well with the results of experiments conducted previously by one of the authors.