This paper aims at establishing the level-one reliability-based design method for evaluating the necessary plate thickness of the cellular-bulkhead quay wall. We evaluated the probability distribution of design parameters by using the results of experiment and field observation. We then evaluated the reliability indices of the plate of cellular-bulkhead quay wall against tensile yield. It was found that reliability indices were very large compared with other structures. We finally evaluated the partial factors for the level-one reliability-based design method.