PURPOSE: To improve the accuracy of fatigue damage evaluation by previously forming standard structures which distinctly indicate the relations between the degrees of fatigue damage and electron microscopic structures in a number of stages.

CONSTITUTION: There are the specified relations between the degrees of the fatigue damages before the generation of cracks and the dislocation structures obtd. from the electron microscopic structures according to the results of the electron microscopic structure analyses of the mechanical parts subjected to the fatigue damages and the thin films of materials which are interrupted of a fatigue test and are given various degrees of the fatigue damages. The standard structures indicating the relations between the degrees of the fatigue damages and the electron microscopic structures in a number of the stages which can be distinctly discriminated are previously formed and a microsample is drawn from the part of the mechanical parts where the fatigue damage is going to be evaluated. The electron microscopic structure of the microsample is then contrasted with the standard structures, by which the degree of the fatigue damage of the mechanical parts can be evaluated. The accuracy of the fatigue damage evaluation is improved in this way.