This paper presents vibration control of a flexible smart beam structure using a new discrete-time sliding mode controller. After formulating the dynamic model in the space representation, so called the separation principle for equivalent controller is established so that the sliding mode conditions are satisfied. By doing this, undesirable chattering of the flexible structures can be attenuated in the settled phase. In order to demonstrate some benefits of the proposed methodology, an experimental realization is undertaken. Both transient and forced vibration control responses are evaluated in time domain and compared between with and without the separation principle.