Cavity modes in Josephson coupled superconductor/insulator superlattices have been studied based on a theoretical model recently proposed by Sakai et al. In such systems the Swihart velocities form a band bounded by two limiting velocities c + and c - corresponding to the in-phase and out-of-phase (in the two neighboring junctions) states, respectively. Cavity modes in stacked double Josephson junctions have also been discussed as a special case.