A stator position adjustment method and device relating to a motor driving device including a motor case, a rotor and a stator disposed on an outer periphery of the rotor concentrically with the rotor, includes adjusting a position of the stator relative to an axial center of the rotor, wherein: the position of the stator relative to the axial center of the rotor is adjusted in a non-inserted state, in which the stator is housed inside the motor case and the rotor is not inserted in the stator, using an adjustment tool, and the adjustment tool is positioned using a rotor shaft-support portion, that shaft-supports the rotor on the motor case as a reference.