The stress distribution in the screw joint is affected by the load distribution on the threads. We performed the fatigue test using five kinds of nuts, i.e. nut of ordinary form with three different heights (8 mm, 5 mm, 3 mm), crown nut, and reversed crown nut for the purpose of different load distribution on the threads. As the results of test, we found the fatigue strength of screw joint decreases according to the increase of m₁, the ratio of the load acting on the first thread to the total load.