A casing for an image-reading device includes a frame made of elongated frame members, such as four frame members that are rigidly connected together. A guide rod may be fixed between a pair of the frame members, and a carriage that supports the optical unit may be guided on the guide rod. A base plate, which is preferably made of glass, is connected to the bottom of the frame. The frame includes shock absorbers distributed evenly around outside side surfaces of the frame or on the bottom of the frame closely adjacent to the outside side surfaces of the frame members. The shock absorbers may be grooves filled with resilient material on the outer sides of the frame members or grooves that are empty or filled with resilient material on the bottoms of the frame members.