A Ru(II)-based metallosupramolecular polymer RuL1 was synthesized by complexation of a Ru(II) salt and phenylenebis(terpyridine). The long polymer chains were observed on a Si substrate using atomic force microscopy. Interestingly, a RuL1 film showed luminescence from the (MLCT)-M-3 state of the Ru(II) complex moieties at room temperature by excitation at the resonant wavelength of the (MLCT)-M-1 absorption. In addition, we fabricated a solid-state polymer device with a RuL1 film and achieved reversible switching of the luminescence by applying voltages (3 and -3 V) between indium tin oxide electrodes, which caused electrochemical redox between Ru(II) and Ru(III).