The invention relates to a scanner's optical device, receive the light coming from the image of an object to be scanned, comprising: several reflective mirrors, a light-focusing module, and a charge coupled device. The reflective mirrors provide reflection and directional change for the light and, by appropriately arranging several reflective mirrors, the light of the object to be scanned directionally changed to a predetermined route. With at least one curving mirror, the light-focusing module focus the light of the predetermined route and then directionally change it, and a raster is then provided in the light route of the curving mirror for filtering out unnecessary light. The charge coupled device may receive the light coming from the light-focusing module and convert it into electronic signals. The said light-focusing module replaces the prior lens set for executing a scanning job.