In this paper, an experimental vehicle with an active suspension system is regarded as a control object. First, a full-vehicle model representing this experimental vehicle was derived, then a control system was designed for this model using the H-infinity control theory. The main purpose of this control system is to achieve robust performance. This control theory has been implemented in an experimental vehicle, and evaluated for robust performance in a four-wheel shaker and during actual driving. It has been confirmed that the desired robust performance is achieved in this closed-loop system.