Abstract: A smart window is provided. The smart window includes an organic light-emitting device including first and second electrodes corresponding to each other, and a light-emitting layer disposed between the first and second electrodes and containing an organic light-emitting material; an electrochromic device including an electrochromic layer containing an electrochromic material and disposed over the organic light-emitting device, wherein the organic light-emitting device is disposed under the electrochromic device to form a light transmission portion in a predetermined region, and wherein the first electrode is formed of a transparent electrode or a high-reflection translucent electrode, and the second electrode is formed of a high-reflection electrode.