Parking Assistance Method and Parking Assistance Device

A parking assistance method includes: detecting, from an image of surroundings of a vehicle, a first target object position; detecting a first image capturing situation when the image is captured; with respect to a second target object position of a target object detected from a past image of surroundings of a target parking position in a past, retrieving one or more combinations of a relative positional relationship between the second target object position and the target parking position and a second image capturing situation when the past image is captured; selecting, the relative positional relationship combined with the second image capturing situation having a difference from the first image capturing situation less than or equal to a predetermined difference; and calculating, based on the selected relative positional relationship and the first target object position, a relative position between a current position of the vehicle and the target parking position.