A seat support suspension improving an absorption characteristic of low-cycle vibrations resulting from rolling. A seat support member supporting a seat is provided via a rolling absorption mechanism for absorbing rolling on brackets as a vehicle body side attachment member attached to the vehicle body side. Thus, rolling, low-cycle vibrations, generated by a phase shift or the like of a hydraulic suspension of the vehicle can be absorbed by the rolling absorption mechanism, a lateral displacement of the body of the seated person can be prevented, stability of a seated posture can be increased, and moreover occurrence of motion sickness can be suppressed.