The purpose of this paper is to make clear the influence of yield stress on the fatigue strength of non-load-carrying fillet welded joints. First of all, brief descriptions about relations between the actual maximum stress considering weld residual stress and the stress range are given, and the combined effect of stress ratio and residual stress is shown. Then, using published fatigue test results, the effect of yield stress on the fatigue strength is studied. In the first step, the results, whose actual maximum stresses are inferred to reach yield stress, are dealt with, and an expression of fatigue strength is obtained. Then, in the next step, the whole data are treated. Finally, the fatigue strength is expressed as follows : Δσ= 33680·σ_r^-0.2282· N _F^-0.3071 +47.76·σ_r^-0.5508· N _F^-0.1249· (σ_r-σ_max') where Δσ is the stress range in MPa, σ_r is the yield stress in MPa, N _F is the number of cycles to failure and σ_max' is the actual maximum stress considering residual stress in MPa. Based on the equation above mentioned, the effect of yield stress on the fatigue strength of welded joints is discussed. The most important finding is ; that, in the case of high tensile residual stress, the fatigue strength of welded joints tends to decrease with increase in yield stress.