In order to evaluate fatigue endurance for the rocker arm of a diesel engine, stress measurements were performed using the strain gages attached near the neck, where is one of the most critical region in the rocker arm, in variation of the engine speed. The fatigue life experiments were carried out on miniature specimens from the rocker arms. For evaluating the fatigue endurance of the rocker arm, the S-N data were compared with the stress analysis results through FEM analysis of the rocker arm. The effective stress of the neck region was determined 17.7MPa through FEM analysis of the rocker arm. Conclusively, on the basis of fatigue limit, the rocker arm has a safety factor of 2.8 or 3.4 from the stress measurement or FEM results, respectively.