1. A vehicle periphery monitoring device which is provided with an imaging unit mounted in a vehicle to image a periphery of the vehicle and is configured to monitor the periphery of the vehicle on the basis of a captured image by the imaging unit, comprising: an object detecting portion configured to detect an object located in an imaging area imaged by the imaging unit; an image processing target area setting portion configured to set an image processing target area which may include an image portion of a monitoring object in the captured image on the basis of a detection result from the object detecting portion; a contour extracting portion configured to extract a contour of the image portion included in the image processing target area; and an object type discriminating portion configured to discriminate a type of the monitoring object in a real space corresponding to the image portion from which the contour has been extracted by the contour extracting portion on the basis of the extracted contour.