Recently, many successful trials for the statistical analysis of irregular ocean waves have been made by oceanographers, such as Pierson, Longuet-Higgins, Neumann and others, while the statistical investigations of the ship motion in irregular seaway have been promoted concurrently under the cooperation of oceanographers and naval architects. Many brilliant results were produced by this cooperation, for instance the papers by Pierson and St. Denis, Lewis and others. The authors have been working on the same problem by model experiments at a seashore, where we built a tower to get a stable platform. From the platform, we measured the waves by a wave recorder, the ship's rolling angle by a pantagraph and the wind pressure by a wind pressure gauge simultaneously, changing the ship's encounter angle and it's natural rolling period. Having applied the statistical analysis to the records obtained, we found that the statistical method given by Longuet-Higgins, Pierson and others gave the outstanding results. Being encouraged by these results, we have tried to extend the same method to a case where irregular wind pressure as well as irregular wave moment affect a ship.