To provide a device for opening/closing a door for a vehicle capable of automatically opening/closing the door for the vehicle by a definite intention of a passenger and having high convenience, and a method for automatically opening/closing the door for the vehicle.

This device is provided with a door opening/closing driving means 40, operation means 15 and 16 for outputting door opening/closing command signals, a vehicle state detection means 70 for outputting a vehicle state signal, a detection means 20 for detecting the door opening/closing command signals and the vehicle state signal, and a control means 30 for controlling the door opening/closing driving means 40. The operation means 15 and 16 are provided at the inside of the vehicle and at the outside of the vehicle, respectively. The control means 30 invalidates the door opening/closing command signal from the operation means 16 at the outside of the vehicle when simultaneously receiving the door opening/closing command signal from the operation means 15 at the inside of the vehicle and the door opening/closing command signal from the operation means 16 at the outside of the vehicle.