Drive device

A drive device according to one embodiment of the present invention is provided with: a motor, which has a rotor having a motor shaft and a rotor body fixed to the motor shaft, and a stator surrounding the rotor; a gear part connected with the motor shaft; and a plurality of bearings that rotatably support the motor shaft. The motor shaft includes: a first shaft fixed to the rotor body; and a second shaft, one side of which is connected to the first shaft and the other side of which is connected to the gear part. One of the first shaft and the second shaft is provided with a spline shaft part, and the spline shaft part is provided with a plurality of external tooth parts on the outer peripheral surface. The other of the first shaft and the second shaft has a spline hole portion into which the spline shaft portion is fitted. The spline hole portion has a plurality of internal tooth portions that mesh with the plurality of external tooth portions on the inner peripheral surface. The gear portion has a helical g