Test results on a free running model of a gigantic ore-carrier are described, in which the hydrodynamic pressures on the hull in oblique waves together with the ship behaviors were measured in order to present the useful materials for the method of wave loads estimation. The behaviors of the gigantic ore-carrier in rough seas, namely speed loss, ship motions and relative water elevations are shown. The distributions of hydrodynamic pressure amplitudes are shown for various wave length and heading angle. In addition to amplitude distributions, phase relations of the hydrodynamic pressures are also shown. Characteristics of the hydrodynamic pressures are explained in connection with the relative water elevations. Comparison between the experimental data and the calculated results obtained by the strip method are made and the usefulness of the strip method for the estimation of the hydrodynamic pressures is discussed.