As a part of labor saving design of ship's hull, usefullness of the straight type structure were investigated. In the Western and the Northern Europe, the ships having straight type structure members have been built. But this type is not generally used, especially in large ships. One of the reason is that the fatigue strength related with the stress intensity of the detailed structural part is not yet known clearly. As for the former research on the straight type structure members, preliminary analysis of the stress and man hour were done at the 110 th division of Japan Ship Research Association and Mitsubishi Heavy Industries, Ltd.. As the result of the research, on type of the structure was picked up as the type of practical use. Our research is composed of Program Fatigue Tests and analysis of the results based on the Linear Fracture Mechanics, and purpose of the research is to estimate the safety of the straight type bracket. The experimental models are 1/2.5 reduced scale of 200, 000 ton tanker's bilge corner and strut end. From the experimental facts and the analytical studies, we may anticipate the practical application of the straight type structure without fatal damages.