A controller controls, based upon a manual operation signal from a first operating means and the automatic operation signal from a second operating means, a driving of a driving power source for generating a driving force for an opening/closing operation of a vehicle door. The controller switches control for driving the driving power source. An automatic operation mode is selected when the automatic operation signal is inputted to the controller, in which the driving power source is driven to output a predetermined first driving output value. A manual operation mode is selected when the manual operation signal is inputted to the controller in which the driving power source is driven to output a second driving output value which is higher than the first driving output value.