Some investigations have been reported about a structural design considering the characteristics of the machine tool joint. From these reports, it may be concluded that the joint is represented by mathematical models consisting of springs and dash-pots. It may, therefore, be said that the problems on the treatment of joints in the computer aided calculation of the structural stiffness are how to decide the spring and damping constants. However even if the basic mathematical model consists of springs and dash-pots, different joints will give various concrete models. It is necessary, for above reasons, to make clear a systematic method of treating the joints. In this report, results of previous studies were accumulated and analyzed to determine the governing factors and propose thereby concrete mathematical models of joints subjected to static load. In addition, some experiments were done to verify their characteristics. From these results, one determination methodology of the mathamatical model for joints was proposed.