Provided is a gear motor including a motor, a speed reducer, a first detector disposition section in which a first rotation detector that detects rotation of a rotor shaft is disposed, a second detector disposition section in which a second rotation detector that detects rotation of an output member of the speed reducer is disposed, and a third detector disposition section in which a torque detector is disposed, in which the gear motor is operable when the first rotation detector is disposed in the first detector disposition section, the second rotation detector is disposed in the second detector disposition section, and the torque detector is disposed in the third detector disposition section, and is operable even when a portion thereof is disposed.