A light modulating device is disclosed herein. In some embodiments, a light modulating device includes a first substrate, a second substrate, and a liquid crystal layer, wherein the liquid crystal layer is disposed between the first and second substrates, and wherein the light modulating device satisfies Equation 1: T2≤3×T1, wherein, T1 is an initial transmittance measured after vertically orienting the liquid crystal layer and placing it between orthogonal polarizers, and T2 is a transmittance measured after heating the liquid crystal layer showing the transmittance of T1 at 100° C. for 5 minutes, and then placing it between the orthogonal polarizers. The light modulating device can stably maintain designed optical properties even after an encapsulation process. The light modulating device can also stably maintain the orientation state of a light modulation layer while effectively securing adhesive force between upper and lower substrates.