To provide a method for easily predicting fatigue strength of a structure.

The stress intensity factor of a crack 20a of focused part 20 of fatigue evaluation is calculated with a finite element method. A part capable of evaluating fatigue strength with nominal stress where a stress distribution by a same load as working on the focused part 20 is determined as a nominal stress part 30. The stress intensity factor of the virtual import crack 30a when virtually importing view crack 20a into the nominal stress section 30 is computed with the finite element method. Then the fatigue strength of the focused part 20 is predicted based on an assumption that a multiplication of the fatigue strength of the focused part 20a and the stress intensity factor, and a multiplication of the fatigue strength of the nominal stress part 30 and the stress intensity factor become constant values equal to each other.