Parking Assistance Method and Parking Assistance Device

A parking assistance method includes: storing positions of target objects detected around the 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, counting the number of times that the learned target object position coincides with a surrounding target object position of a target object detected around the own vehicle and providing a higher degree of reliability to the learned target object position having a larger 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 with a position of a target object detected around the own vehicle, calculating a relative position of the own vehicle with respect to the target parking position.