Metal nanoparticle array shows surface lattice plasmon mode which can confine the light energy into the 2-dimensional space. Effective utilization of light energy could be realized if molecule excitons are strongly coupled with plasmons in the structures. When the energy level of molecules located near the metal nanoparticles are close to that of plasmon, the strong coupling forms, resulting in the new energy state formation. In this study, we have controlled the coupling strength between Au lattice structure and organic dye molecules via electrochemical method.