In our previous paper, a cummulative damage law for the prediction of fatigue life was proposed and in this report, to study a effect of mean stress and a fatigue strength reduction factor, the cummulative damage law was applied to plane, notched and butt welded specimens under axial loaded condition. σ _a -σ _m diagram and σ_-1/σ₀- N diagram were obtained by the cummulative damage law and experimental results, where σ _a , σ _m are stress amplitude and mean stress respectively, σ_-1, σ₀ are fatigue strength with stress ratio-1 and 0 respectively, and N is number of cycles. σ _a -σ _m diagram is expressed by two straight line segments σ_-1-σ₀ and σ₀-σ _B . Relation between σ_-1/σ₀and N is expressed the form of σ_-1/σ₀=α· N ^β, and constants α, β are as follows. for plane specimen ; α=2, β=-0.0353, 10⁰≤ N ≤2×10⁶ for notched and butt welded specimens ; α=2, β=-0.0753, 10⁰≤ N ≤10⁴ α=1, β=0, 10⁴< N Using the above σ _a -σ _m diagram, σ _-1 /σ ₀ - N diagram and one S-N diagram, S-N diagrams with arbitary mean stress or stress ratio can be obtained, and from these S-N diagrams, fatigue strength reduction factor may be estimated.