Parking Assistance Method and Parking Assistance Device

A parking assistance device comprising:

• a sensor configured to detect a target object position, the target object position being a position of a target object around an own vehicle;
• and
• a controller configured to:
• store positions of a plurality of target objects detected around the target parking position when the own vehicle is parked at a target parking position as learned target object positions;
• when the own vehicle travels in a vicinity of the target parking position after the learned target object positions are stored, count, with respect to each of the plurality of learned target object positions, a number of times that the learned target object position coincides with a surrounding target object position, the surrounding target object position being a position of a target object detected around the own vehicle;
• provide a higher degree of reliability to the learned target object position having a large number of times of coincidence with the surrounding target object position than to the learned target object position having a small number of times of coincidence with the surrounding target object position;
• by comparing the learned target object position having a degree of reliability greater than or equal to a predetermined threshold degree of reliability among the learned target object positions with a target object position detected around the own vehicle, calculate a relative position of an own vehicle with respect to the target parking position;
• based on the calculated relative position, calculate a target travel trajectory from a current position of the own vehicle to the target parking position;
• and
• performs parking assistance control to assist movement of the own vehicle along the calculated target travel trajectory.