An optical device including a bearing structure and a light-transmitting plate body is provided. The bearing structure includes a first frame body and a second frame body connected to each other, and the first frame body is located in the second frame body. The first frame body has at least one first inner surface, and the at least one first inner surface has at least one limiting protruding portion protruding from the at least one first inner surface. The light-transmitting plate body is disposed in the first frame body and is fixed to the first frame body. The light-transmitting plate body has at least one first edge, and the at least one first edge of the light-transmitting plate body is positioned through the at least one limiting protruding portion.