We report a visible light-induced reversible photomagnetism in Cu-2(II)[Mo-IV(CN)(8)]. 8H(2)O (1). By the irradiation with a 480-nm laser light, the compound 1 showed a spontaneous magnetization with a magnetic ordering temperature (T-c) of 30 K. Conversely, the magnetization and T-c values were reduced by the irradiation with a 600-nm laser light. This photomagnetism is due to the reversible photo-induced electron transfer between paramagnetic 1 and its valence isomer exhibiting ferromagnetism.