This paper describes the applicability of Level II method in reliability engineering to ship strength design and two application examples. In the case of non-buckling-damaged upper deck plates, the safety index is greater than 4. In addition, the buckling strength reliability of upper deck plates does not decrease even if ship design philosophy changes from use of mild steel to use of high-tensile-strength steel. On the other hand, in the case of fatigue-damaged cruciform joints, the critical safety index was estimated to be about 3.13.6. Furthermore, effect of load probability distribution on the fatigue strength reliability was also made clear. Finally, the partial-safety-factor design formulas were derived for the buckling strength and the fatigue strength of ship structures considering the safety index.