Premium threaded joints, which have some particular structures, are generally used to connect pipe-structures in the sea. As these joints suffer not only external/internal pressure but also tensioning and bending loads, it is important to know their mechanical behavior for the structural design. However, most of previous studies have been developed on the basis of some numerical analysis methods (such as FEM) to estimate the distribution of stresses or strains at the most critical parts, i. e., the thread roots, and it is so difficult to find out studies which discuss this problem by experimental methods. In this study, direct measuring of the axial strains at the thread roots was carried out both through Make-Up test and tensioning test, with a view to show the strain distribution of a threaded joint. For comparative studies, approximate analyses by a FEM program were also done, and the results were compared with the experimental data. First, it was found that the strain amplitude at the first thread root of Pin, which resulted from the tensile load, was drastically constrained owing to the Make-Up operation ; Make-Up proved to be effective to improve the fatigue strength of threaded joints. Secondly, actual strain distribution at the thread roots of Pin was not so smooth as the ordinary FEM results for every case, showing a fairly wide scatter band. As the extent of this scatter was almost equivalent to a extremely poor contact case which was simulated by FEM calculation, it was concluded that the effect of poor contact at the threads must be taken into account in analyzing threaded joints numerically.