1. A vehicle surroundings monitoring device comprising: imaging unit which is mounted in a vehicle and captures an image of surroundings of the vehicle; and an image processing unit having a processor and a memory, the image processing unit being configured to: extract an image area for a predetermined part of a desired type of object in the captured image; extract, on the basis of a predetermined area below the extracted image area, a candidate for a desired type of object; determine, for each object candidate extracted, whether the object candidate is the desired type of object; and exclude an object in the image area from candidates for the desired type of object when no pattern different from a background is captured in the predetermined area, or when a pattern different from the background is captured only in one of a first and a second areas each of which is a half of the predetermined area divided in a horizontal direction.