To provide a dimming device that can adjust the transmissivity of light up to approximately 100%, and secure a sufficient visual field at need.

This device is equipped with inside and outside light scatter plates 16 and 17, which are formed of light-transmissive materials and provided with a convex lens part 29 and a concave lens part 30, a holding frame 14, which holds them movably opposite each other, and a driving means, which moves at least one of the inside and outside light scatter plates relatively to the other. When the inside and outside light scatter plates are positioned so that the lens parts of the same kind face each other, the device enters a light transmission state, wherein incident light is transmitted through the inside and outside light scatter plates without being scattered. When the inside and outside light scatter plates are so positioned that different kind of lens parts face each other, the device enters a light scatter state wherein the incident light is scattered.