A gear motor (100) is provided with a motor (102), a decelerator (104), an output shaft of the decelerator (104) coupled to a driven shaft of a driving roller (116), and a torque arm (106) for preventing rotation of the gear motor (100) around the driven shaft. One end (106a) of the torque arm (106) is fixed to the gear motor (100) and the other end (106b) is fixed to an installation seat (120). The torque arm (106) is provided with a damper mechanism (108).
