Electric-field effect on the confined minigap states in coupled semiconductor superlattices is studied theoretically. Due to the perturbation of periodicity in the superlattice by an applied field, delocalization of the confined states is observed. In the weak field regime, delocalization of the minigap states is similar to the quantum confined Stark effect in single quantum wells. In the strong field regime, confined states disappear. and addtional states from the original superlattice miniband are introduced to form semibound states due to the mixing of localized Stark ladders with the gap mode. Our numerical simulation will have an impact on confirmation of the propsed confined states in experimental observations. Possible device applications are discussed.