An optical device includes a supporting frame and a light-transmissive element. The supporting frame has a frame body defining a through hole, and an extending portion extending from a side of the frame body and having a first cutting edge. The light-transmissible element is disposed on the supporting frame and has a main body aligned with the through hole, and an extending portion extending from a side of the main body and aligned with the extending portion of the supporting frame. The extending portion of the light-transmissible element has a second cutting edge that is flush with the first cutting edge of the supporting frame.