Fatigue design method of steel bellows damper during earthquake excitations is examined. Bellows dampers are connected between a girder and an abutment in order to reduce damage of superstructures and substructures. Low-cycle fatigue properties of the bellows damper are examined based on low cycle fatigue tests of the bellows damper and nonlinear dynamic response analyses of girder bridges with the bellows damper connected at both ends. Fatigue strength of the bellows is evaluated using P/V difference method which is one of cycle counting methods and Miner's cumulative damage law. Fatigue damage evaluation is performed by three methods using plastic strains，total displacements and plastic displacements of the bellows dampers as indices respectively. Further，a damage index based on cumulative plastic displacements is proposed. Validity of the proposed damage index is verified compared with the three methods of fatigue damage evaluation.
