A perimeter monitoring device is applied to a vehicle comprising a distance measuring sensor for transmitting a probing wave and receiving a reflected wave of the probing wave and an imaging device for capturing an image of the surroundings of the vehicle. The perimeter monitoring device comprises: an information acquisition unit for acquiring distance information, directional information, and object width information of an object existing in the vicinity of the vehicle as detection information of the object provided by the distance measuring sensor; an area setting unit for setting an image processing area on which image processing is performed in the image captured by the imaging device based on the distance information, the directional information, and the object width information acquired by the information acquisition unit; and an object recognition unit for performing the image processing on the image processing area set by the area setting unit to recognize the object.