In this paper robust stability and robust performance between an ordinary H-infinity controller and μ-controller are compared for the case of vibration control of a flexible structure using two active dynamic vibration absorbers. The structure possesses eight transverse-torsional coupled vibration modes, and the aim of this study is to reduce transverse and torsional vibrations simultaneously. After some control experiments were carried out, it was confirmed that the μ-controller shows better robust stability and robust performance than an ordinary H-infinity controller