Experimental studies were carried out to examine the influence of undercut depth at the weld toe on the fatigue strength. Non-load carrying cruciform and T fillet welded joints were tested and quantitative life reductions due to undercut were obtained. Test results and life estimation procedure were reported in the previous paper. In this report, the fatigue strengths for 2 × 10⁶ cycles were studied and were compared with each other. Adding to 16 test series joints concerning to undercuts, 40 test joints having various fillet shapes were also analysed. The equivalent fatigue strengths for 2 × 10⁶ cycles were calculated from each failure life of test data, referring to the estimated S·N relations of these joints. The joint strengths were evaluated through the mean and the standard deviation of these equivalent strengths. The influence of the undercut depth and the bead toe shapes could quantitatively be discussed considering the undercut dependence of estimated strength as well as the scatter of equivalent strength data. These results led to the draft of the acceptance level that the allowable maximum undercut depth is 0.3 mm for the special members of offshore structures.