Operation assistance system and operation assistance method

An operation assistance method for assisting an operation for a first on-vehicle device of a first vehicle, the operation assistance method comprising:

• a step of, by a recording unit, recording a relative position of an operation unit of a second vehicle with respect to the second vehicle, and a second on-vehicle device of the second vehicle that is operated by using the operation unit, while associating the relative position with the second on-vehicle device;
• a motion recognition step of, by a calculation unit, recognizing a predetermined motion of a hand of a vehicle occupant in the first vehicle;
• a position recognition step of, by the calculation unit, recognizing a first relative position corresponding to a relative position of the hand of the vehicle occupant with respect to the first vehicle;
• a specifying step of, by the calculation unit, specifying the second on-vehicle device of the second vehicle that is operated by using the operation unit of the second vehicle provided at a second relative position, on a basis of a record in the recording unit, the second relative position being a relative position with respect to the second vehicle and corresponding to the first relative position;
• and
• a control step of, by the calculation unit, assisting the operation for the first on-vehicle device of the first vehicle, the first on-vehicle device including a function common with that of the second on-vehicle device.