The present application relates to a transmittance-variable device and a use thereof. The transmittance-variable device of the present application can switch between a clear state and a black state, can exhibit high transmittance in the clear state and a high shielding rate in the black state, and can exhibit a high contrast ratio even at the inclination angle. Such a transmittance-variable device of the present application can be applied to various applications including various architectural or automotive materials which need to adjust the transmittance, or eyewear such as goggles for augmented reality experience or sports, sunglasses or helmets.
