An image processing device includes: a delimiting line detection unit configured to detect a delimiting line candidate based on image data obtained by capturing a surrounding of a vehicle, the delimiting line candidate being a candidate of a delimiting line that delimits a parking space; and an exclusion determination unit configured to determine whether or not to exclude the delimiting line candidate detected by the delimiting line detection unit from the candidate of the delimiting line. In a case where a plurality of the delimiting line candidates is detected within a predetermined range in the image data, the exclusion determination unit determines whether or not to exclude the delimiting line candidate from the candidate of the delimiting line by comparing edge strength of the plurality of delimiting line candidates.