1. A vehicle periphery monitoring device configured to recognize a monitoring object in the periphery of a self vehicle on the basis of a captured image by a vehicular camera, comprising: a light image portion extraction unit configured to extract a first image portion having a feature quantity of a light of a vehicle from the captured image; an expanded region setting unit configured to set a region which has a predefined size and contains the first image portion as a first expanded region; and an object class recognition unit configured to determine whether or not the first expanded region has a bilateral symmetry in the horizontal direction with the first image portion as the central point, and recognize an image containing the light image portion as the image of another vehicle when the first expanded region is determined to have a bilateral symmetry.