In a rotor mechanism of a rotating electrical machine, a crimp groove is formed, in a circumferential direction, in an outer circumferential portion of any one of the end plates of a rotor shaft on an outside in the axial direction. The one end plate is located in the axial direction by an inside end of a crimp retainer in the axial direction that is ring-shaped, that covers the crimp groove of the rotor shaft to fit to the rotor shaft, that is fitted into the crimp groove of the rotor shaft by crimping an outside portion in the axial direction from an outer circumferential side and that engages with a wall surface of the crimp groove on the outside in the axial direction.