Parking Assistance Method and Parking Assistance Device

A parking assistance method includes: calculating a first target travel trajectory starting from a start point of an actual travel trajectory when a vehicle is parked by manual driving and reaching a target parking position; calculating a deviation range including a portion of the actual travel trajectory in which the actual travel trajectory deviates a first predetermined distance or more from the first target travel trajectory; setting a target intermediate position existing in the deviation range; when assisting the vehicle in parking at the target parking position, calculating a second target travel trajectory, that is a trajectory starting from a parking start position, the parking start position being a position of the vehicle at a time point when parking is started, passing through the target intermediate position, and reaching the target parking position; and performing parking assistance control to assist the vehicle in moving along the second target travel trajectory.