An optical system includes an photographic lens, a fiber optical plate, and an image pickup member. The photographic lens forms the first image in the vicinity of the entrance end surface of the fiber optical plate, and after the first image is transmitted through the fiber optical plate, the second image is formed in the vicinity of the exit end surface of the fiber optical plate. The image pickup member is disposed to coincide in size with the second image. The first image is demagnified to a desired image size determined by the image pickup member and thereby the photographic lens is downsized.