The purpose of this study is to clarify the time history of wave-induced stress by analyzing data collected from 6 naval ships over a period of 3 years. The time history of wave-induced stress at midship deck plate is compared with encountered wave height condition. By the data, wave-induced stress is linear to wave height in the elastic stress region. The property of the time history of wave-induced stress, therefore, is considered to be the same as that of encountered wave condition. The proposed random fatigue loading model based on the encountered wave conditions can be verified by the data from time history of wave-induced stress. Based on the above result, the random fatigue loading model for ship structural members is discussed.