The invention relates to an eccentric-motor-excited bending-torsion coupled resonance type residual stress eliminating device. Torsion vibration output by a torsion exciter excited by an eccentric motor is applied to a high-stiffness rotating rotary shaft. When the rotation frequency of the rotary shaft is equal to the difference between the bending inherent frequency and the torsion inherent frequency, according to the bending-torsion coupled resonance theory, the torsion vibration excitation with the frequency equal to the torsion inherent frequency can excite bending resonance at the same time, the bending resonance and the torsion resonance enhance each other, and enough dynamic stress is generated to eliminate the residual stress of the high-stiffness rotating shaft. The eccentric-motor-excited bending-torsion coupled resonance type residual stress eliminating device solves the problem that bending-torsion coupled resonance vibration stress relief is restrained by a torsion vibration excitation source, the residual stress of the high-stiffness rotating shaft is eliminated through the bending-torsion coupled resonance excited by the eccentric motor, and the efficiency is improved; and the eccentric-motor-excited bending-torsion coupled resonance type residual stress eliminating device is simple and compact in structure, more convenient to implement and more reliable in work performance.