According to the present invention, in a rotational fluctuation reducing apparatus, a serial connection formed, via an intermediate retainer 36, between a low-rigidity first coil spring 32 and a high-rigidity second coil spring 34 is disposed between the first retainer 16 and the second retainer 18 which form a pair, which are spaced apart from each other in the circumferential direction, and which are made of resin material. The first coil spring 32 and the intermediate retainer 36 are disposed in a bottomed recess 40 of the first retainer 16. During deformation, the intermediate retainer 36 is caused to slide at a radially outer portion of the bottomed recess 40 of the first retainer 16. The second coil spring 34 is contained in a bottomed recess 42 of the second retainer 18. Damping control is performed, in a low-torque range, under low torsional rigidity resulting from the serial connection of the first coil spring 32 and the second coil spring 34, and is performed, in a normal torque range, under high torsional rigidity provided solely by the second coil spring 34. The present invention achieves reduction in abnormal noise due to switching taking place through resin-metal contact and low noise during the idling.

In a method of assembling a damper device, a first support portion of a first rotor and a first accommodation portion of a second rotor are overlapped to eliminate an axial offset between them. A first elastic member is placed in the first support portion and the first accommodation portion. A second support portion of the first rotor and a second accommodation portion of the second rotor are overlapped to eliminate an axial offset between them by simultaneously compressing the first elastic member and rotating the second rotor relative to the first rotor to a first-side in a rotational direction. A second elastic member is placed in the second support portion and the second accommodation portion. Simultaneously, the second elastic member is compressed and the second rotor is rotated relative to the first rotor to a second-side in the rotational direction by angle corresponding to the offset between the first support portion and the first accommodation portion.