The authors measured ship motions and the vomiting ratio of passengers on a crusise ship in one week voyage. The results demonstrate that it is possible to estimate the vomiting ration in fairly good accuracy by the author's estimation method on the bases of O'Hanlon's experimental data. However, when the passengers are exposed to severe ship motions more than one day, the estimated vomiting ratio after then show an overestimation due to the habituation effect. A decrease function of vomiting ratio with time which shows habituation effect is obtained from the results of the present experiment. The vomiting ratio estimated using the function is in fairly good agreement with the results of actual vomiting ratio.