A driving apparatus comprising: an input shaft with a hollow space formed therein; a motor configured to rotate the input shaft about a rotation axis along the axial direction; a reduction gear arranged on one side of the motor, the reduction gear being configured to receive power of the motor from the input shaft; an output shaft inserted through the hollow space of the input shaft, the output shaft being adapted to rotate about the rotation axis with power output from the reduction gear; a coupling connected to a tip end of the output shaft on the one side of the motor so as to transmit the power output from the reduction gear to the output shaft; and a detector provided on the other side of the motor, the detector being configured to detect information on rotation of the input shaft and information on rotation of the output shaft, wherein: a first bearing adapted to support the output shaft is arranged on said other side of the motor, and a second bearing adapted to support the output shaft is arranged on said one side of the motor characterized in that the second bearing is arranged in the hollow space between the input shaft and the output shaft;; and the output shaft is rotatably supported on the input shaft by the second bearing, and the output shaft is attachable to and detachable from the coupling while being coupled to the input shaft. an input shaft with a hollow space formed therein; a motor configured to rotate the input shaft about a rotation axis along the axial direction; a reduction gear arranged on one side of the motor, the reduction gear being configured to receive power of the motor from the input shaft; an output shaft inserted through the hollow space of the input shaft, the output shaft being adapted to rotate about the rotation axis with power output from the reduction gear; a coupling connected to a tip end of the output shaft on the one side of the motor so as to transmit the power output from the reduction gear to the output shaft; and a detector provided on the other side of the motor, the detector being configured to detect information on rotation of the input shaft and information on rotation of the output shaft, wherein: a first bearing adapted to support the output shaft is arranged on said other side of the motor, and a second bearing adapted to support the output shaft is arranged on said one side of the motor characterized in that the second bearing is arranged in the hollow space between the input shaft and the output shaft;; and the output shaft is rotatably supported on the input shaft by the second bearing, and the output shaft is attachable to and detachable from the coupling while being coupled to the input shaft. a first bearing adapted to support the output shaft is arranged on said other side of the motor, and a second bearing adapted to support the output shaft is arranged on said one side of the motor characterized in that the second bearing is arranged in the hollow space between the input shaft and the output shaft;; and the output shaft is rotatably supported on the input shaft by the second bearing, and the output shaft is attachable to and detachable from the coupling while being coupled to the input shaft.