To restrain a resonant vibration of a coil spring 56 provided on a cushion unit 40 without having the large-sized coil spring and complicated assembling operation.

A cylindrical elastic sheet 57 having a notch slit 58a is arranged between an outer shaft member 51 of a damper set 53 and the coil spring 56, and the elastic sheet 57 is urged to an opening direction by an elastic ring 62 which is arranged on the point of the elastic sheet. Thus, vibrations of the coil spring 56 is restrained by making the elastic sheet 57 keep into contact with the coil spring 56 vibrated with travelling vibrations of a vehicle. The cushion unit 40 is not enlarged so that the elastic sheet 57 is arranged on the inside of the coil spring 56 in the cushion unit, and the cushion unit 40 can be assembled without any complicated operation.