Parking Assistance Method and Parking Assistance Device

A parking assistance device comprising:

• an image capturing device configured to capture surroundings of an own vehicle;
• and
• a controller configured to:
• detect a first target object position, the first target object position being a position of a target object around the own vehicle, from an image generated by the image capturing device;
• detect a first image capturing situation, the first image capturing situation being an image capturing situation when the image is captured;
• with respect to a second target object position, the second target object position being a target object position of a target object detected from a past image, the past image being an image acquired by capturing surroundings of a target parking position in a past, retrieve, from a predetermined storage device in which 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, the second image capturing situation being image capturing situation when the past image is captured, are stored, one or more combinations of the relative positional relationship and the second image capturing situation;
• select, among the retrieved relative positional relationships, the relative positional relationship stored in combination with the second image capturing situation having a difference from the first image capturing situation less than or equal to a predetermined difference;
• and
• calculate, based on the selected relative positional relationship and the first target object position, a relative position between a current position of the own vehicle and the target parking position.