Through the previous papers, the authors presented a method of predicting nonlinear wave loads acting on a ship in large-amplitude waves, and verified its validity for evaluating nonlinearities of wave loads to a satisfactory extent in both quantitative and qualitative sense. Furthermore, this paper deals with nonlinear wave loads of a ship in most general case, that is to say, wave loads on a free-sailing ship in large amplitude waves, and effects of ship's advance speed on their nonlinearities are investigated in detail. Vertical wave loads are more sensitive to wave height compared with lateral wave loads except torsional moment. Computed results of vertical wave loads agree well with experimental results, and clarify that a main reason of the nonlinearity of vertical wave loads is time-varying relative vertical displacement of a ship and that the nonlinear coupling between vertical and horizontal hydrodynamic forces come to be important at and near the frequency of roll resonance. For the nonlinearity of torsional moment, the above-mentioned coupling effect plays a dominant role in relatively short waves where roll is small. It is also found that as the ship's speed increases, in general, nonlinear component of vertical wave loads increases remarkably so that the peak values of nonlinear wave loads may exceed by far the peak values obtained by linear calculation. The almost same trend is found in torsional moment while the effect of ship speed is negligible for horizontal shear force and horizontal bending moment.